SQL数据库英文文献及翻译

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SQL数据库外文翻译--数据库的工作

Working with DatabasesThis chapter describes how to use SQL statements in embedded applications to control databases. There are three database statements that set up and open databases for access: SET DATABASE declares a database handle, associates the handle with an actual database file, and optionally assigns operational parameters for the database.SET NAMES optionally specifies the character set a client application uses for CHAR, VARCHAR, and text Blob data. The server uses this information totransli terate from a database‟s default character set to the client‟s character set on SELECT operations, and to transliterate from a client application‟s character set to the database character set on INSERT and UPDATE operations.g CONNECT opens a database, allocates system resources for it, and optionally assigns operational parameters for the database.All databases must be closed before a program ends. A database can be closed by using DISCONNECT, or by appending the RELEASE option to the final COMMIT or ROLLBACK in a program. Declaring a databaseBefore a database can be opened and used in a program, it must first be declared with SET DATABASE to:CHAPTER 3 WORKING WITH DATABASES. Establish a database handle. Associate the database handle with a database file stored on a local or remote node.A database handle is a unique, abbreviated alias for an actual database name. Database handles are used in subsequent CONNECT, COMMIT RELEASE, and ROLLBACK RELEASE statements to specify which databases they should affect. Except in dynamic SQL (DSQL) applications, database handles can also be used inside transaction blocks to qualify, or differentiate, table names when two or more open databases contain identically named tables.Each database handle must be unique among all variables used in a program. Database handles cannot duplicate host-language reserved words, and cannot be InterBase reserved words.The following statement illustrates a simple database declaration:EXEC SQLSET DATABASE DB1 = ‟employee.gdb‟;This database declaration identifies the database file, employee.gdb, as a database the program uses, and assigns the database a handle, or alias, DB1.If a program runs in a directory different from the directory that contains the database file, then the file name specification in SET DATABASE must include a full path name, too. For example, the following SET DATABASE declaration specifies the full path to employee.gdb:EXEC SQLSET DATABASE DB1 = ‟/interbase/examples/employee.gdb‟;If a program and a database file it uses reside on different hosts, then the file name specification must also include a host name. The following declaration illustrates how a Unix host name is included as part of the database file specification on a TCP/IP network:EXEC SQLSET DATABASE DB1 = ‟jupiter:/usr/interbase/examples/employee.gdb‟;On a Windows network that uses the Netbeui protocol, specify the path as follows: EXEC SQLSET DATABASE DB1 = ‟//venus/C:/Interbase/examples/employee.gdb‟; DECLARING A DATABASEEMBEDDED SQL GUIDE 37Declaring multiple databasesAn SQL program, but not a DSQL program, can access multiple databases at the same time. In multi-database programs, database handles are required. A handle is used to:1. Reference individual databases in a multi-database transaction.2. Qualify table names.3. Specify databases to open in CONNECT statements.Indicate databases to close with DISCONNECT, COMMIT RELEASE, and ROLLBACK RELEASE.DSQL programs can access only a single database at a time, so database handle use is restricted to connecting to and disconnecting from a database.In multi-database programs, each database must be declared in a separate SET DATABASE statement. For example, the following code contains two SET DATABASE statements:. . .EXEC SQLSET DATABASE DB2 = ‟employee2.gdb‟;EXEC SQLSET DATABASE DB1 = ‟employee.gdb‟;. . .4Using handles for table namesWhen the same table name occurs in more than one simultaneously accessed database, a database handle must be used to differentiate one table name from another. The database handle is used as a prefix to table names, and takes the formhandle.table.For example, in the following code, the database handles, TEST and EMP, are used to distinguish between two tables, each named EMPLOYEE:. . .EXEC SQLDECLARE IDMATCH CURSOR FORSELECT TESTNO INTO :matchid FROM TEST.EMPLOYEEWHERE TESTNO > 100;EXEC SQLDECLARE EIDMATCH CURSOR FORSELECT EMPNO INTO :empid FROM EMP.EMPLOYEEWHERE EMPNO = :matchid;. . .CHAPTER 3 WORKING WITH DATABASES38 INTERBASE 6IMPORTANTThis use of database handles applies only to embedded SQL applications. DSQL applications cannot access multiple databases simultaneously.4Using handles with operationsIn multi-database programs, database handles must be specified in CONNECT statements to identify which databases among several to open and prepare for use in subsequent transactions.Database handles can also be used with DISCONNECT, COMMIT RELEASE, and ROLLBACKRELEASE to specify a subset of open databases to close.To open and prepare a database w ith CONNECT, see “Opening a database” on page 41.To close a database with DISCONNECT, COMMIT RELEASE, or ROLLBACK RELEASE, see“Closing a database” on page 49. To learn more about using database handles in transactions, see “Accessing an open database” on p age 48.Preprocessing and run time databasesNormally, each SET DATABASE statement specifies a single database file to associate with a handle. When a program is preprocessed, gpre uses the specified file to validate the program‟s table and column referenc es. Later, when a user runs the program, the same database file is accessed. Different databases can be specified for preprocessing and run time when necessary.4Using the COMPILETIME clause A program can be designed to run against any one of several identically structured databases. In other cases, the actual database that a program will use at runtime is not available when a program is preprocessed and compiled. In such cases, SET DATABASE can include a COMPILETIME clause to specify a database for gpre to test against during preprocessing. For example, the following SET DATABASE statement declares that employee.gdb is to be used by gpre during preprocessing: EXEC SQLSET DATABASE EMP = COMPILETIME ‟employee.gdb‟;IMPORTANTThe file specification that follows the COMPILETIME keyword must always be a hard-coded, quoted string.DECLARING A DATABASEEMBEDDED SQL GUIDE 39When SET DATABASE uses the COMPILETIME clause, but no RUNTIME clause, and does not specify a different database file specification in a subsequent CONNECT statement, the same database file is used both for preprocessing and run time. To specify different preprocessing and runtime databases with SET DATABASE, use both the COMPILETIME andRUNTIME clauses.4Using the RUNTIME clauseWhen a database file is specified for use during preprocessing, SET DATABASE can specify a different database to use at run time by including the RUNTIME keyword and a runtime file specification:EXEC SQLSET DATABASE EMP = COMPILETIME ‟employee.gdb‟RUNTIME ‟employee2.gdb‟;The file specification that follows the RUNTIME keyword can be either ahard-coded, quoted string, or a host-language variable. For example, the following C code fragment prompts the user for a database name, and stores the name in a variable that is used later in SET DATABASE:. . .char db_name[125];. . .printf("Enter the desired database name, including node and path):\n");gets(db_name);EXEC SQLSET DATABASE EMP = COMPILETIME ‟employee.gdb‟ RUNTIME : db_name; . . .Note host-language variables in SET DATABASE must be preceded, as always, by a colon.Controlling SET DATABASE scopeBy default, SET DATABASE creates a handle that is global to all modules in an application.A global handle is one that may be referenced in all host-language modules comprising the program. SET DATABASE provides two optional keywords to change the scope of a declaration:g STATIC limits declaration scope to the module containing the SET DATABASE statement. No other program modules can see or use a database handle declared STATIC.CHAPTER 3 WORKING WITH DATABASES40 INTERBASE 6EXTERN notifies gpre that a SET DATABASE statement in a module duplicates a globally-declared database in another module. If the EXTERN keyword is used, then another module must contain the actual SET DATABASE statement, or an error occurs during compilation.The STATIC keyword is used in a multi-module program to restrict database handle access to the single module where it is declared. The following example illustrates the use of theSTATIC keyword:EXEC SQLSET DATABASE EMP = STATIC ‟employee.gdb‟;The EXTERN keyword is used in a multi-module program to signal that SET DATABASE in one module is not an actual declaration, but refers to a declaration made in a different module. Gpre uses this information during preprocessing. The following example illustrates the use of the EXTERN keyword:EXEC SQLSET DATABASE EMP = EXTERN ‟employee.gdb‟;If an application contains an EXTERN reference, then when it is used at run time, the actual SET DATABASE declaration must be processed first, and the database connected before other modules can access it.A single SET DATABASE statement can contain either the STATIC or EXTERN keyword, but not both. A scope declaration in SET DATABASE applies to both COMPILETIME and RUNTIME databases.Specifying a connection character setWhen a client application connects to a database, it may have its own character set requirements. The server providing database access to the client does not know about these requirements unless the client specifies them. The client application specifies its character set requirement using the SET NAMES statement before it connects to the database.SET NAMES specifies the character set the server should use when translating data from the database to the client application. Similarly, when the client sends data to the database, the server translates the data from the client‟s character set to the database‟s default character set (or the character set for an individual column if it differs from the databas e‟s default character set). For example, the following statements specify that the client is using the DOS437 character set, then connect to the database:EXEC SQLOPENING A DATABASEEMBEDDED SQL GUIDE 41SET NAMES DOS437;EXEC SQLCONNECT ‟europe.gdb‟ USER ‟JAMES‟ PASSWORD ‟U4EEAH‟;For more information about character sets, see the Data Definition Guide. For the complete syntax of SET NAMES and CONNECT, see the Language Reference. Opening a databaseAfter a database is declared, it must be attached with a CONNECT statement before it can be used. CONNECT:1. Allocates system resources for the database.2. Determines if the database file is local, residing on the same host where the application itself is running, or remote, residing on a different host.3. Opens the database and examines it to make sure it is valid.InterBase provides transparent access to all databases, whether local or remote. If the database structure is invalid, the on-disk structure (ODS) number does not correspond to the one required by InterBase, or if the database is corrupt, InterBase reports an error, and permits no further access. Optionally, CONNECT can be used to specify:4. A user name and password combination that is checked against the server‟s security database before allowing the connect to succeed. User names can be up to 31 characters.Passwords are restricted to 8 characters.5. An SQL role name that the user adopts on connection to the database, provided that the user has previously been granted membership in the role. Regardless of role memberships granted, the user belongs to no role unless specified with this ROLE clause.The client can specify at most one role per connection, and cannot switch roles except by reconnecting.6. The size of the database buffer cache to allocate to the application when the default cache size is inappropriate.Using simple CONNECT statementsIn its simplest form, CONNECT requires one or more database parameters, each specifying the name of a database to open. The name of the database can be a: Database handle declared in a previous SET DATABASE statement.CHAPTER 3 WORKING WITH DATABASES42 INTERBASE 61. Host-language variable.2. Hard-coded file name.4Using a database handleIf a program uses SET DATABASE to provide database handles, those handles should be used in subsequent CONNECT statements instead of hard-coded names. For example,. . .EXEC SQLSET DATABASE DB1 = ‟employee.gdb‟;EXEC SQLSET DATABASE DB2 = ‟employee2.gdb‟;EXEC SQLCONNECT DB1;EXEC SQLCONNECT DB2;. . .There are several advantages to using a database handle with CONNECT:1. Long file specifications can be replaced by shorter, mnemonic handles.2. Handles can be used to qualify table names in multi-database transactions. DSQL applications do not support multi-database transactions.3. Handles can be reassigned to other databases as needed.4. The number of database cache buffers can be specified as an additional CONNECT parameter.For more information about setting the number of database cache buffers, see “Setting d atabase cache buffers” on page 47. 4Using strings or host-language variables Instead of using a database handle, CONNECT can use a database name supplied at run time. The database name can be supplied as either a host-language variable or a hard-coded, quoted string.The following C code demonstrates how a program accessing only a single database might implement CONNECT using a file name solicited from a user at run time:. . .char fname[125];. . .printf(‟Enter the desired database name, including nodeand path):\n‟);OPENING A DATABASEEMBEDDED SQL GUIDE 43gets(fname);. . .EXEC SQLCONNECT :fname;. . .TipThis technique is especially useful for programs that are designed to work with many identically structured databases, one at a time, such as CAD/CAM or architectural databases.MULTIPLE DATABASE IMPLEMENTATIONTo use a database specified by the user as a host-language variable in a CONNECT statement in multi-database programs, follow these steps:1. Declare a database handle using the following SET DATABASE syntax:EXEC SQLSET DATABASE handle = COMPILETIME ‟ dbname‟;Here, handle is a hard-coded database handle supplied by the programmer, dbnameis a quoted, hard-coded database name used by gpre during preprocessing.2. Prompt the user for a database to open.3. Store the database name entered by the user in a host-language variable.4. Use the handle to open the database, associating the host-language variable with the handle using the following CONNECT syntax:EXEC SQLCONNECT : variable AS handle;The following C code illustrates these steps:. . .char fname[125];. . .EXEC SQLSET DATABASE DB1 = ‟employee.gdb‟;printf("Enter the desired database name, including nodeand path):\n");gets(fname);EXEC SQLCONNECT :fname AS DB1;. . .CHAPTER 3 WORKING WITH DATABASES44 INTERBASE 6In this example, SET DATABASE provides a hard-coded database file name for preprocessing with gpre. When a user runs the program, the database specified in the variable, fname, is used instead. 4Using a hard-coded database namesIN SINGE-DATABASE PROGRAMSIn a single-database program that omits SET DATABASE, CONNECT must contain a hard-coded, quoted file name in the following format:EXEC SQLCONNECT ‟[ host[ path]] filename‟; host is required only if a program and a dat abase file it uses reside on different nodes.Similarly, path is required only if the database file does not reside in the current working directory. For example, the following CONNECT statement contains ahard-coded file name that includes both a Unix host name and a path name:EXEC SQLCONNECT ‟valdez:usr/interbase/examples/employee.gdb‟;Note Host syntax is specific to each server platform.IMPORTANT A program that accesses multiple databases cannot use this form of CONNECT.IN MULTI-DATABASE PROGRAMSA program that accesses multiple databases must declare handles for each of them in separate SET DATABASE statements. These handles must be used in subsequent CONNECT statements to identify specific databases to open:. . .EXEC SQLSET DATABASE DB1 = ‟employee.gdb‟;EXEC SQLSET DATABASE DB2 = ‟employee2.gdb‟;EXEC SQLCONNECT DB1;EXEC SQLCONNECT DB2;. . .Later, when the program closes these databases, the database handles are no longer in use. These handles can be reassigned to other databases by hard-coding a file name in a subsequent CONNECT statement. For example,OPENING A DATABASEEMBEDDED SQL GUIDE 45. . .EXEC SQLDISCONNECT DB1, DB2;EXEC SQLCONNECT ‟project.gdb‟ AS DB1;. . .Additional CONNECT syntaxCONNECT supports several formats for opening databases to provide programming flexibility. The following table outlines each possible syntax, provides descriptions and examples, and indicates whether CONNECT can be used in programs that access single or multiple databases:For a complete discussion of CONNECT syntax and its uses, see the Language Reference.Syntax Description ExampleSingle accessMultiple accessCONNECT …dbfile‟; Opens a single, hard-coded database file, dbfile.EXEC SQLCONNECT …employee.gdb‟;Yes NoCONNECT handle; Opens the database file associated with a previously declared database handle. This is the preferred CONNECT syntax.EXEC SQLCONNECT EMP;Yes YesCONNECT …dbfile‟ AS handle;Opens a hard-coded database file, dbfile, and assigns a previously declared database handle to it.EXEC SQLCONNECT …employee.gdb‟AS EMP;Yes Yes CONNECT :varname AS handle;Opens the database file stored in the host-language variable, varname, and assigns a previously declared database handle to it.EXEC SQL CONNECT :fname AS EMP;Yes YesTABLE 3.1 CONNECT syntax summaryCHAPTER 3 WORKING WITH DATABASES46 INTERBASE 6Attaching to multiple databasesCONNECT can attach to multiple databases. To open all databases specified in previous SETDATABASE statements, use either of the following CONNECT syntax options: EXEC SQLCONNECT ALL;EXEC SQLCONNECT DEFAULT;CONNECT can also attach to a specified list of databases. Separate each database request from others with commas. For example, the following statement opens two databases specified by their handles:EXEC SQLCONNECT DB1, DB2;The next statement opens two hard-coded database files and also assigns them to previously declared handles:EXEC SQLCONNECT ‟employee.gdb‟ AS DB1, ‟employee2.gdb‟ AS DB2;Tip Opening multiple databases with a single CONNECT is most effective when a program‟s database access is simple and clear. In complex programs that open and close several databases, that substitute database names with host-language variables, or that assign multiple handles to the same database, use separate CONNECT statements to make program code easier to read, debug, and modify.Handling CONNECT errors. The WHENEVER statement should be used to trap and handle runtime errors that occur during database declaration. The following C code fragment illustrates an error-handling routine that displays error messages and ends the program in an orderly fashion:. . .EXEC SQLWHENEVER SQLERRORGOTO error_exit;. . .OPENING A DATABASEEMBEDDED SQL GUIDE 47:error_exitisc_print_sqlerr(sqlcode, status_vector);EXEC SQLDISCONNECT ALL;exit(1);. . .For a complete discussion of SQL error handling, see Chapter 12, “Error Handling and Recovery.”数据库的工作这章描述怎样使用在嵌入式应用过程中的SQL语句控制数据库。

外文翻译原文-Appropriate Uses For SQLite

毕业设计（论文）——外文翻译（原文）Appropriate Uses For SQLiteSQLite is different from most other SQL database engines in that its primary design goal is to be simple:●Simple to administer●Simple to operate●Simple to embed in a larger program●Simple to maintain and customizeMany people like SQLite because it is small and fast. But those qualities are just happy accidents. Users also find that SQLite is very reliable. Reliability is a consequence of simplicity. With less complication, there is less to go wrong. So, yes, SQLite is small, fast, and reliable, but first and foremost, SQLite strives to be simple.Simplicity in a database engine can be either a strength or a weakness, depending on what you are trying to do. In order to achieve simplicity, SQLite has had to sacrifice other characteristics that some people find useful, such as high concurrency, fine-grained access control, a rich set of built-in functions, stored procedures, esoteric SQL language features, XML and/or Java extensions, tera- or peta-byte scalability, and so forth. If you need some of these features and do not mind the added complexity that they bring, then SQLite is probably not the database for you. SQLite is not intended to be an enterprise database engine. It is not designed to compete with Oracle or PostgreSQL.The basic rule of thumb for when it is appropriate to use SQLite is this: Use SQLite in situations where simplicity of administration, implementation, and maintenance are more important than the countless complex features that enterprise database engines provide. As it turns out, situations where simplicity is the better choice are more common than many people realize.Another way to look at SQLite is this: SQLite is not designed to replace Oracle. It is designed to replace fopen( ).Situations Where SQLite Works W ell●Application File FormatSQLite has been used with great success as the on-disk file format for desktop applications such as financial analysis tools, CAD packages, record keeping programs, and so forth. The traditional File/Open operation does an sqlite3_open() and executes a BEGIN TRANSACTION to get exclusive access to the content. File/Save does a COMMIT followed by another BEGIN TRANSACTION. The use of transactions guarantees that updates to the application file are atomic, durable, isolated, and consistent.Temporary triggers can be added to the database to record all changes into a (temporary) undo/redo log table. These changes can then be played back when the user presses the Undo and Redo buttons. Using this technique, an unlimited depth undo/redo implementation can be written in surprisingly little code.●Embedded devices and applicationsBecause an SQLite database requires little or no administration, SQLite is a good choice for devices or services that must work unattended and without human support. SQLite is a good fit foruse in cellphones, PDAs, set-top boxes, and/or appliances. It also works well as an embedded database in downloadable consumer applications.●WebsitesSQLite usually will work great as the database engine for low to medium traffic websites (which is to say, 99.9% of all websites). The amount of web traffic that SQLite can handle depends, of course, on how heavily the website uses its database. Generally speaking, any site that gets fewer than 100K hits/day should work fine with SQLite. The 100K hits/day figure is a conservative estimate, not a hard upper bound. SQLite has been demonstrated to work with 10 times that amount of traffic.●Replacement for ad hoc disk filesMany programs use fopen( ), fread( ), and fwrite( ) to create and manage files of data in home-grown formats. SQLite works particularly well as a replacement for these ad hoc data files.●Internal or temporary databasesFor programs that have a lot of data that must be sifted and sorted in diverse ways, it is often easier and quicker to load the data into an in-memory SQLite database and use queries with joins and ORDER BY clauses to extract the data in the form and order needed rather than to try to code the same operations manually. Using an SQL database internally in this way also gives the program greater flexibility since new columns and indices can be added without having to recode every query.●Command-line dataset analysis toolExperienced SQL users can employ the command-line sqlite program to analyze miscellaneous datasets. Raw data can be imported from CSV files, then that data can be sliced and diced to generate a myriad of summary reports. Possible uses include website log analysis, sports statistics analysis, compilation of programming metrics, and analysis of experimental results.Y ou can also do the same thing with an enterprise client/server database, of course. The advantages to using SQLite in this situation are that SQLite is much easier to set up and the resulting database is a single file that you can store on a floppy disk or flash-memory stick or email to a colleague.●Stand-in for an enterprise database during demos or testingIf you are writing a client application for an enterprise database engine, it makes sense to use a generic database backend that allows you to connect to many different kinds of SQL database engines. It makes even better sense to go ahead and include SQLite in the mix of supported databases and to statically link the SQLite engine in with the client. That way the client program can be used standalone with an SQLite data file for testing or for demonstrations.●Database PedagogyBecause it is simple to setup and use (installation is trivial: just copy the sqlite or sqlite.exe executable to the target machine and run it) SQLite makes a good database engine for use in teaching SQL. Students can easily create as many databases as they like and can email databases to the instructor for comments or grading. For more advanced students who are interested in studying how an RDBMS is implemented, the modular and well-commented and documented SQLite code can serve as a good basis. This is not to say that SQLite is an accurate model of how other database engines are implemented, but rather a student who understands how SQLite works can more quickly comprehend the operational principles of other systems.●Experimental SQL language extensionsThe simple, modular design of SQLite makes it a good platform for prototyping new, experimental database language features or ideas.Situations Where Another RDBMS May Work Better●Client/Server ApplicationsIf you have many client programs accessing a common database over a network, you should consider using a client/server database engine instead of SQLite. SQLite will work over a network filesystem, but because of the latency associated with most network filesystems, performance will not be great. Also, the file locking logic of many network filesystems implementation contains bugs (on both Unix and Windows). If file locking does not work like it should, it might be possible for two or more client programs to modify the same part of the same database at the same time, resulting in database corruption. Because this problem results from bugs in the underlying filesystem implementation, there is nothing SQLite can do to prevent it.A good rule of thumb is that you should avoid using SQLite in situations where the same database will be accessed simultaneously from many computers over a network filesystem.●High-volume WebsitesSQLite will normally work fine as the database backend to a website. But if you website is so busy that you are thinking of splitting the database component off onto a separate machine, then you should definitely consider using an enterprise-class client/server database engine instead of SQLite.●Very large datasetsWith the default page size of 1024 bytes, an SQLite database is limited in size to 2 terabytes (241 bytes). And even if it could handle larger databases, SQLite stores the entire database in a single disk file and many filesystems limit the maximum size of files to something less than this. So if you are contemplating databases of this magnitude, you would do well to consider using a client/server database engine that spreads its content across multiple disk files, and perhaps across multiple volumes.●High ConcurrencySQLite uses reader/writer locks on the entire database file. That means if any process is reading from any part of the database, all other processes are prevented from writing any other part of the database. Similarly, if any one process is writing to the database, all other processes are prevented from reading any other part of the database. For many situations, this is not a problem. Each application does its database work quickly and moves on, and no lock lasts for more than a few dozen milliseconds. But there are some applications that require more concurrency, and those applications may need to seek a different solution.出处：/whentouse.html。

数据库中英文对照外文翻译文献

中英文对照外文翻译Database Management SystemsA database (sometimes spelled data base) is also called an electronic database , referring to any collection of data, or information, that is specially organized for rapid search and retrieval by a computer. Databases are structured to facilitate the storage, retrieval , modification, and deletion of data in conjunction with various data-processing operations .Databases can be stored on magnetic disk or tape, optical disk, or some other secondary storage device.A database consists of a file or a set of files. The information in these files may be broken down into records, each of which consists of one or more fields. Fields are the basic units of data storage , and each field typically contains information pertaining to one aspect or attribute of the entity described by the database . Using keywords and various sorting commands, users can rapidly search , rearrange, group, and select the fields in many records to retrieve or create reports on particular aggregate of data.Complex data relationships and linkages may be found in all but the simplest databases .The system software package that handles the difficult tasks associated with creating ,accessing, and maintaining database records is called a database management system(DBMS).The programs in a DBMS package establish an interface between the database itself and the users of the database.. (These users may be applications programmers, managers and others with information needs, and various OS programs.)A DBMS can organize, process, and present selected data elements form the database. This capability enables decision makers to search, probe, and query database contents in order to extract answers to nonrecurring and unplanned questions that aren’t available in regular reports. These questions might initially be vague and/or poorly defined ,but people can “browse” through the database until they have the needed information. In short, the DBMS will “manage” the stored data items and assemble the needed items from the common database in response to the queries of those who aren’t programmers.A database management system (DBMS) is composed of three major parts:(1)a storage subsystemthat stores and retrieves data in files;(2) a modeling and manipulation subsystem that provides the means with which to organize the data and to add , delete, maintain, and update the data;(3)and an interface between the DBMS and its users. Several major trends are emerging that enhance the value and usefulness of database management systems;Managers: who require more up-to-data information to make effective decisionCustomers: who demand increasingly sophisticated information services and more current information about the status of their orders, invoices, and accounts.Users: who find that they can develop custom applications with database systems in a fraction of the time it takes to use traditional programming languages.Organizations : that discover information has a strategic value; they utilize their database systems to gain an edge over their competitors.The Database ModelA data model describes a way to structure and manipulate the data in a database. The structural part of the model specifies how data should be represented(such as tree, tables, and so on ).The manipulative part of the model specifies the operation with which to add, delete, display, maintain, print, search, select, sort and update the data.Hierarchical ModelThe first database management systems used a hierarchical model-that is-they arranged records into a tree structure. Some records are root records and all others have unique parent records. The structure of the tree is designed to reflect the order in which the data will be used that is ,the record at the root of a tree will be accessed first, then records one level below the root ,and so on.The hierarchical model was developed because hierarchical relationships are commonly found in business applications. As you have known, an organization char often describes a hierarchical relationship: top management is at the highest level, middle management at lower levels, and operational employees at the lowest levels. Note that within a strict hierarchy, each level of management may have many employees or levels of employees beneath it, but each employee has only one manager. Hierarchical data are characterized by this one-to-many relationship among data.In the hierarchical approach, each relationship must be explicitly defined when the database is created. Each record in a hierarchical database can contain only one key field and only one relationship is allowed between any two fields. This can create a problem because data do not always conform to such a strict hierarchy.Relational ModelA major breakthrough in database research occurred in 1970 when E. F. Codd proposed a fundamentally different approach to database management called relational model ,which uses a table asits data structure.The relational database is the most widely used database structure. Data is organized into related tables. Each table is made up of rows called and columns called fields. Each record contains fields of data about some specific item. For example, in a table containing information on employees, a record would contain fields of data such as a person’s last name ,first name ,and street address.Structured query language(SQL)is a query language for manipulating data in a relational database .It is nonprocedural or declarative, in which the user need only specify an English-like description that specifies the operation and the described record or combination of records. A query optimizer translates the description into a procedure to perform the database manipulation.Network ModelThe network model creates relationships among data through a linked-list structure in which subordinate records can be linked to more than one parent record. This approach combines records with links, which are called pointers. The pointers are addresses that indicate the location of a record. With the network approach, a subordinate record can be linked to a key record and at the same time itself be a key record linked to other sets of subordinate records. The network mode historically has had a performance advantage over other database models. Today , such performance characteristics are only important in high-volume ,high-speed transaction processing such as automatic teller machine networks or airline reservation system.Both hierarchical and network databases are application specific. If a new application is developed ,maintaining the consistency of databases in different applications can be very difficult. For example, suppose a new pension application is developed .The data are the same, but a new database must be created.Object ModelThe newest approach to database management uses an object model , in which records are represented by entities called objects that can both store data and provide methods or procedures to perform specific tasks.The query language used for the object model is the same object-oriented programming language used to develop the database application .This can create problems because there is no simple , uniform query language such as SQL . The object model is relatively new, and only a few examples of object-oriented database exist. It has attracted attention because developers who choose an object-oriented programming language want a database based on an object-oriented model. Distributed DatabaseSimilarly , a distributed database is one in which different parts of the database reside on physically separated computers . One goal of distributed databases is the access of informationwithout regard to where the data might be stored. Keeping in mind that once the users and their data are separated , the communication and networking concepts come into play .Distributed databases require software that resides partially in the larger computer. This software bridges the gap between personal and large computers and resolves the problems of incompatible data formats. Ideally, it would make the mainframe databases appear to be large libraries of information, with most of the processing accomplished on the personal computer.A drawback to some distributed systems is that they are often based on what is called a mainframe-entire model , in which the larger host computer is seen as the master and the terminal or personal computer is seen as a slave. There are some advantages to this approach . With databases under centralized control , many of the problems of data integrity that we mentioned earlier are solved . But today’s personal computers, departmental computers, and distributed processing require computers and their applications to communicate with each other on a more equal or peer-to-peer basis. In a database, the client/server model provides the framework for distributing databases.One way to take advantage of many connected computers running database applications is to distribute the application into cooperating parts that are independent of one anther. A client is an end user or computer program that requests resources across a network. A server is a computer running software that fulfills those requests across a network . When the resources are data in a database ,the client/server model provides the framework for distributing database.A file serve is software that provides access to files across a network. A dedicated file server is a single computer dedicated to being a file server. This is useful ,for example ,if the files are large and require fast access .In such cases, a minicomputer or mainframe would be used as a file server. A distributed file server spreads the files around on individual computers instead of placing them on one dedicated computer.Advantages of the latter server include the ability to store and retrieve files on other computers and the elimination of duplicate files on each computer. A major disadvantage , however, is that individual read/write requests are being moved across the network and problems can arise when updating files. Suppose a user requests a record from a file and changes it while another user requests the same record and changes it too. The solution to this problems called record locking, which means that the first request makes others requests wait until the first request is satisfied . Other users may be able to read the record, but they will not be able to change it .A database server is software that services requests to a database across a network. For example, suppose a user types in a query for data on his or her personal computer . If the application is designed with the client/server model in mind ,the query language part on the personal computer simple sends the query across the network to the database server and requests to be notified when the data are found.Examples of distributed database systems can be found in the engineering world. Sun’s Network Filing System(NFS),for example, is used in computer-aided engineering applications to distribute data among the hard disks in a network of Sun workstation.Distributing databases is an evolutionary step because it is logical that data should exist at the location where they are being used . Departmental computers within a large corporation ,for example, should have data reside locally , yet those data should be accessible by authorized corporate management when they want to consolidate departmental data . DBMS software will protect the security and integrity of the database , and the distributed database will appear to its users as no different from the non-distributed database .In this information age, the data server has become the heart of a company. This one piece of software controls the rhythm of most organizations and is used to pump information lifeblood through the arteries of the network. Because of the critical nature of this application, the data server is also the one of the most popular targets for hackers. If a hacker owns this application, he can cause the company's "heart" to suffer a fatal arrest.Ironically, although most users are now aware of hackers, they still do not realize how susceptible their database servers are to hack attacks. Thus, this article presents a description of the primary methods of attacking database servers (also known as SQL servers) and shows you how to protect yourself from these attacks.You should note this information is not new. Many technical white papers go into great detail about how to perform SQL attacks, and numerous vulnerabilities have been posted to security lists that describe exactly how certain database applications can be exploited. This article was written for the curious non-SQL experts who do not care to know the details, and as a review to those who do use SQL regularly.What Is a SQL Server?A database application is a program that provides clients with access to data. There are many variations of this type of application, ranging from the expensive enterprise-level Microsoft SQL Server to the free and open source mySQL. Regardless of the flavor, most database server applications have several things in common.First, database applications use the same general programming language known as SQL, or Structured Query Language. This language, also known as a fourth-level language due to its simplistic syntax, is at the core of how a client communicates its requests to the server. Using SQL in its simplest form, a programmer can select, add, update, and delete information in a database. However, SQL can also be used to create and design entire databases, perform various functions on the returned information, and even execute other programs.To illustrate how SQL can be used, the following is an example of a simple standard SQL query and a more powerful SQL query:Simple: "Select * from dbFurniture.tblChair"This returns all information in the table tblChair from the database dbFurniture.Complex: "EXEC master..xp_cmdshell 'dir c:\'"This short SQL command returns to the client the list of files and folders under the c:\ directory of the SQL server. Note that this example uses an extended stored procedure that is exclusive to MS SQL Server.The second function that database server applications share is that they all require some form of authenticated connection between client and host. Although the SQL language is fairly easy to use, at least in its basic form, any client that wants to perform queries must first provide some form of credentials that will authorize the client; the client also must define the format of the request and response.This connection is defined by several attributes, depending on the relative location of the client and what operating systems are in use. We could spend a whole article discussing various technologies such as DSN connections, DSN-less connections, RDO, ADO, and more, but these subjects are outside the scope of this article. If you want to learn more about them, a little Google'ing will provide you with more than enough information. However, the following is a list of the more common items included in a connection request.Database sourceRequest typeDatabaseUser IDPasswordBefore any connection can be made, the client must define what type of database server it is connecting to. This is handled by a software component that provides the client with the instructions needed to create the request in the correct format. In addition to the type of database, the request type can be used to further define how the client's request will be handled by the server. Next comes the database name and finally the authentication information.All the connection information is important, but by far the weakest link is the authentication information—or lack thereof. In a properly managed server, each database has its own users with specifically designated permissions that control what type of activity they can perform. For example, a user account would be set up as read only for applications that need to only access information. Another account should be used for inserts or updates, and maybe even a third account would be used for deletes.This type of account control ensures that any compromised account is limited in functionality. Unfortunately, many database programs are set up with null or easy passwords, which leads to successful hack attacks.译文数据库管理系统介绍数据库（database,有时拼作data base）又称为电子数据库，是专门组织起来的一组数据或信息，其目的是为了便于计算机快速查询及检索。

外文文献-中文翻译-数据库

外文文献-中文翻译-数据库英文原文2:《DBA Survivor: Become a Rock Star DBA》by Thomas LaRock，Published By Apress.2010You know that a database is a collection of logically related data elements that may be structured in various ways lo meet the multiple processing and retrieval needs of organizations and individuals. There’s nothing new about databases—early ones were chiseled in stone, penned on scrolls, and written on index cards. But now databases are commonly recorded on magnetizable media, and computer programs are required to perform the necessary storage and retrieval operations.Yo u’ll see in the following pages that complex data relationships and linkages may be found in all but the simplest databases. The system software package that handles the difficult tasks associated with creating, accessing, and maintaining database records is called a database management system (DBMS) .The programs in a DBMS package establish an interface between the database itself and the users of the database. (These users may be applications programmers, managers and others with information needs, and various OS programs.)A DBMS can organize, process, and present selected data elements from the database. This capability enables decision makers to search, probe, and query database contents in order to extract answers to nonrecurring and unplanned questions (hat aren't available in regular reports. These questions might initially be vague and / or poorly defined, but peo ple can "browse” through the database until they have the needed information. Inshort, the DBMS will “m anage”the stored data items and assemble the needed items from the common database in response to the queries of those who aren’t10programmers. In a file-oriented system, users needing special information may communicate their needs to a programmer, who, when time permits, will write one or more programs to extract the data and prepare the information[4].The availability of a DBMS, however, offers users a much faster alternative communications path.If the DBMS provides a way to interactively and update the database, as well as interrogate it capability allows for managing personal data-Aces however, it does not automatically leave an audit trail of actions and docs not provide the kinds of control a necessary in a multiuser organization. These-controls arc only available when a set of application programs arc customized for each data entry and updating function.Software for personal computers which perform me of the DBMS functions have been very popular. Personal computers were intended for use by individuals for personal information storage and process- These machines have also been used extensively small enterprises, professionals like doctors, acrylics, engineers, lasers and so on .By the nature of intended usage, database systems on these machines except from several of the requirements of full doge database systems. Since data sharing is not tended, concurrent operations even less so. the fewer can be less complex. Security and integrity maintenance arc de-emphasized or absent. As data limes will be small, performance efficiency is also important. In fact, the only aspect of a database system that is important is data Independence. Data-dependence, as stated earlier, means that applicant programs and user queries need not recognizant physical organization of data on secondary storage. The importance of this aspect, particularly for the personal computer user, is that this greatly simplifies database usage. The user can store, access and manipulate data a( a high level (close to (he application) and be totally shielded from the10low level (close to the machine) details of data organization. We will not discuss details of specific PC DBMS software packages here. Let us summarize in the following the strengths and weaknesses of personal computer data-base software systems：The most obvious positive factor is the user friendliness of the software. A user with no prior computer background would be able to use the system to store personal and professional data, retrieve and perform relayed processing. The user should, of course, satiety himself about the quality of software and the freedom from errors (bugs) so that invest-merits in data arc protected.For the programmer implementing applications with them, the advantage lies in the support for applications development in terms of input screen generations, output report generation etc. offered by theses stems.The main negative point concerns absence of data protection features. Unless encrypted, data cane accessed by whoever has access to the machine Data can be destroyed through mistakes or malicious intent. The second weakness of many of the PC-based systems is that of performance. If data volumes grow up to a few thousands of records, performance could be a bottleneck.For organization where growth in data volumes is expected, availability of. the same or compatible software on large machines should be considered.This is one of the most common misconceptions about database management systems that are used in personal computers. Thoroughly comprehensive and sophisticated business systems can be developed in dBASE, Paradox and other DBMSs. However, they are created by experienced programmers using the DBMS's own programming language. Thai is not the same as users who create and manage personal10files that are not part of the mainstream company system.Transaction Management of DatabaseThe objective of long-duration transactions is to model long-duration, interactive Database access sessions in application environments. The fundamental assumption about short-duration of transactions that underlies the traditional model of transactions is inappropriate for long-duration transactions. The implementation of the traditional model of transactions may cause intolerably long waits when transactions aleph to acquire locks before accessing data, and may also cause a large amount of work to be lost when transactions are backed out in response to user-initiated aborts or system failure situations.The objective of a transaction model is to pro-vide a rigorous basis for automatically enforcing criterion for database consistency for a set of multiple concurrent read and write accesses to the database in the presence of potential system failure situations. The consistency criterion adopted for traditional transactions is the notion of scrializability. Scrializa-bility is enforced in conventional database systems through theuse of locking for automatic concurrency control, and logging for automatic recovery from system failure situations. A “transaction’’ that doesn't provide a basis for automatically enforcing data-base consistency is not really a transaction. To be sure, a long-duration transaction need not adopt seri-alizability as its consistency criterion. However, there must be some consistency criterion.Version System Management of DatabaseDespite a large number of proposals on version support in the context of computer aided design and software engineering, the absence of a consensus on version semantics10has been a key impediment to version support in database systems. Because of the differences between files and databases, it is intuitively clear that the model of versions in database systems cannot be as simple as that adopted in file systems to support software engineering.For data-bases, it may be necessary to manage not only versions of single objects (e.g. a software module, document, but also versions of a collection of objects (e.g. a compound document, a user manual, etc. and perhaps even versions of the schema of database (c.g. a table or a class, a collection of tables or classes).Broadly, there arc three directions of research and development in versioning. First is the notion of a parameterized versioning", that is, designing and implementing a versioning system whose behavior may be tailored by adjusting system parameters This may be the only viable approach, in view of the fact that there are various plausible choices for virtually every single aspect of versioning.The second is to revisit these plausible choices for every aspect of versioning, with the view to discardingsome of themes either impractical or flawed. The third is the investigation into the semantics and implementation of versioning collections of objects and of versioning the database.There is no consensus of the definition of the te rm “management information system”. Some writers prefer alternative terminology such as “information processing system”， "information and decision syste m, “organizational information syste m”, or simply “i nformat ion system” to refer to the computer-based information processing system which supports the operations, management, and decision-making functions of an organization. This text uses “MIS” because i t is descriptive and generally understood; it also frequently uses "information system”instead of ''MIS” t o refer to an organizational information system.10A definition of a management information system, as the term is generally understood, is an integrated, user-machine system for providing information 丨o support operations, management, and decision-making functions in an organization. The system utilizes computer hardware and software; manual procedures: models for analysis planning, control and decision making; and a database. The fact that it is an integrated system does not mean that it is a single, monolithic structure: rather, ii means that the parts fit into an overall design. The elements of the definition arc highlighted below: Computer-based user-machine system.Conceptually, a management information can exist without computer, but it is the power of the computer which makes MIS feasible. The question is not whether computers should be used in management information system, but the extent to whichinformation use should be computerized. The concept of a user-machine system implies that some (asks are best performed humans, while others are best done by machine. The user of an MIS is any person responsible for entering input da(a, instructing the system, or utilizing the information output of the system. For many problems, the user and the computer form a combined system with results obtained through a set of interactions between the computer and the user.User-machine interaction is facilitated by operation in which the user's input-output device (usually a visual display terminal) is connected lo the computer. The computer can be a personal computer serving only one user or a large computer that serves a number of users through terminals connected by communication lines. The user input-output device permits direct input of data and immediate output of results. For instance, a person using The computer interactively in financial planning poses 4t what10if* questions by entering input at the terminal keyboard; the results are displayed on the screen in a few second.The computer-based user-machine characteristics of an MIS affect the knowledge requirements of both system developer and system user, “computer-based” means that the designer of a management information system must have a knowledge of computers and of their use in processing. The “user-machine” concept means the system designer should also understand the capabilities of humans as system components (as information processors) and the behavior of humans as users of information.Information system applications should not require users Co be computer experts. However, users need to be able lo specify(heir information requirements; some understanding of computers, the nature of information, and its use in various management function aids users in this task.Management information system typically provide the basis for integration of organizational information processing. Individual applications within information systems arc developed for and by diverse sets of users. If there are no integrating processes and mechanisms, the individual applications may be inconsistent and incompatible. Data item may be specified differently and may not be compatible across applications that use the same data. There may be redundant development of separate applications when actually a single application could serve more than one need. A user wanting to perform analysis using data from two different applications may find the task very difficult and sometimes impossible.The first step in integration of information system applications is an overall information system plan. Even though application systems are implemented one at a10time, their design can be guided by the overall plan, which determines how they fit in with other functions. In essence, the information system is designed as a planed federation of small systems.Information system integration is also achieved through standards, guidelines, and procedures set by the MIS function. The enforcement of such standards and procedures permit diverse applications to share data, meet audit and control requirements, and be shares by multiple users. For instance, an application may be developed to run on a particular small computer. Standards for integration may dictate that theequipment selected be compatible with the centralized database. The trend in information system design is toward separate application processing form the data used to support it. The separate database is the mechanism by which data items are integrated across many applications and made consistently available to a variety of users. The need for a database in MIS is discussed below.The term “information” and “data” are frequently used interchangeably; However, information is generally defined as data that is meaningful or useful to The recipient. Data items are therefore the raw material for producing information.The underlying concept of a database is that data needs to be managed in order to be available for processing and have appropriate quality. This data management includes both software and organization. The software to create and manage a database is a database management system.When all access to any use of database is controlled through a database management system, all applications utilizing a particular data item access the same data item which is stored in only one place. A single updating of the data item updates it for10all uses. Integration through a database management system requires a central authority for the database. The data can be stored in one central computer or dispersed among several computers; the overriding requirement is that there be an organizational function to exercise control.It is usually insufficient for human recipients to receive only raw data or even summarized data. Data usually needs to be processed and presented in such a way that Che result is directed toward the decision to be made. To do this, processing of dataitems is based on a decision model.For example, an investment decision relative to new capital expenditures might be processed in terms of a capital expenditure decision model.Decision models can be used to support different stages in the decision-making process. “Intelligence’’ models can be used to search for problems and/or opportunities. Models can be used to identify and analyze possible solutions. Choice models such as optimization models maybe used to find the most desirable solution.In other words, multiple approaches are needed to meet a variety of decision situations. The following are examples and the type of model that might be included in an MIS to aid in analysis in support of decision-making; in a comprehensive information system, the decision maker has available a set of general models that can be applied to many analysis and decision situations plus a set of very specific models for unique decisions. Similar models are available tor planning and control. The set of models is the model base for the MIS.Models are generally most effective when the manager can use interactive dialog (o build a plan or to iterate through several decision choices under different conditions.10中文译文2:《数据库幸存者：成为一个摇滚名明星》众所周知，数据库是逻辑上相关的数据元的汇集.这些数据元可以按不同的结构组织起来，以满足单位和个人的多种处理和检索的需要。

SQL数据库中英文对照外文翻译文献

SQL数据库中英文对照外文翻译文献中英文对照外文翻译文献(文档含英文原文和中文翻译)Working with DatabasesThis chapter describes how to use SQL statements in embedded applications to control databases. There are three database statements that set up and open databases for access: SET DATABASE declares a database handle, associates the handle with an actual database file, and optionally assigns operational parameters for the database.SET NAMES optionally specifies the character set a client application uses for CHAR, VARCHAR, and text Blob data. The server uses this information to transliterate from a database?s default character set to the client?s character set on SELECT operations, and to transliterate from a client application?s character set to the database character set on INSERT and UPDATE operations.g CONNECT opens a database, allocates system resources for it, and optionally assigns operational parameters for the database.All databases must be closed before a program ends. A database can be closed by using DISCONNECT, or by appending the RELEASE option to the final COMMIT or ROLLBACK in a program.Declaring a databaseBefore a database can be opened and used in a program, it must first be declared with SET DATABASE to:CHAPTER 3 WORKING WITH DATABASES. Establish a database handle. Associate the database handle with a database file stored on a local or remote node.A database handle is aunique, abbreviated alias for an actual database name. Database handles are used in subsequent CONNECT, COMMIT RELEASE, and ROLLBACK RELEASE statements to specify which databases they should affect. Except in dynamic SQL (DSQL) applications, database handles can also be used inside transaction blocks to qualify, or differentiate, table names when two or more open databases contain identically named tables.Each database handle must be unique among all variables used in a program. Database handles cannot duplicate host-language reserved words, and cannot be InterBase reserved words.The following statement illustrates a simple database declaration:EXEC SQLSET DATABASE DB1 = ?employee.gdb?;This database declaration identifies the database file, employee.gdb, as a database the program uses, and assigns the database a handle, or alias, DB1.If a program runs in a directory different from the directory that contains the database file, then the file name specification in SET DATABASE must include a full path name, too. For example, the following SET DATABASE declaration specifies the full path to employee.gdb:EXEC SQLSET DATABASE DB1 = ?/interbase/examples/employee.gdb?;If a program and a database file it uses reside on different hosts, then the file name specification must also include a host name. The following declaration illustrates how a Unix host name is included as part of the database file specification on a TCP/IP network:EXEC SQLSET DATABASE DB1 = ?jupiter:/usr/interbase/examples/employee.gdb?;On a Windows network that uses the Netbeui protocol, specify the path as follows: EXEC SQLSET DATABASE DB1 = ?//venus/C:/Interbase/examples/employee.gdb?; DECLARING A DATABASEEMBEDDED SQL GUIDE 37Declaring multiple databasesAn SQL program, but not a DSQL program, can access multiple databases at the same time. In multi-database programs, database handles are required. A handle is used to:1. Reference individual databases in a multi-database transaction.2. Qualify table names.3. Specify databases to open in CONNECT statements.Indicate databases to close with DISCONNECT, COMMIT RELEASE, and ROLLBACK RELEASE.DSQL programs can access only a single database at a time, so database handle use is restricted to connecting to and disconnecting from a database.In multi-database programs, each database must be declared in a separate SET DATABASE statement. For example, the following code contains two SET DATABASE statements: . . .EXEC SQLSET DATABASE DB2 = ?employee2.gdb?;EXEC SQLSET DATABASE DB1 = ?employee.gdb?;. . .4Using handles for table namesWhen the same table name occurs in more than one simultaneously accessed database, a database handle must be used to differentiate one table name from another. The database handle is used as a prefix to table names, and takes the form handle.table.For example, in the following code, the database handles, TEST and EMP, are used to distinguish between two tables, each named EMPLOYEE:. . .EXEC SQLDECLARE IDMATCH CURSOR FORSELECT TESTNO INTO :matchid FROM TEST.EMPLOYEEWHERE TESTNO > 100;EXEC SQLDECLARE EIDMATCH CURSOR FORSELECT EMPNO INTO :empid FROM EMP.EMPLOYEEWHERE EMPNO = :matchid;. . .CHAPTER 3 WORKING WITH DATABASES38 INTERBASE 6IMPORTANTThis use of database handles applies only to embedded SQL applications. DSQL applications cannot access multiple databases simultaneously.4Using handles with operationsIn multi-database programs, database handles must be specified in CONNECT statements to identify which databases among several to open and prepare for use in subsequent transactions.Database handles can also be used with DISCONNECT, COMMIT RELEASE, and ROLLBACKRELEASE to specify a subset of open databases to close.To open and prepare a database with CONNECT, see “Opening a database” on page 41.To close a database with DISCONNECT, COMMIT RELEASE, or ROLLBACK RELEASE, see“Closing a database” on page 49. To learn more about using database handles in transactions, see “Accessing an open database” on page 48.Preprocessing and run time databasesNormally, each SET DATABASE statement specifies a single database file to associate with a handle. When a program is preprocessed, gpre uses the specified file to validate the prog ram?s table and column references. Later, when a user runs the program, the same database file is accessed. Different databases can be specified for preprocessing and run time when necessary.4Using the COMPILETIME clause A program can be designed to run against any one of several identically structured databases. In other cases, the actual database that a program will use at runtime is not available when a program is preprocessed and compiled. In such cases, SET DATABASE can include a COMPILETIME clause to specify a database for gpre to test against during preprocessing. For example, the following SET DATABASE statement declares that employee.gdb is to be used by gpre during preprocessing: EXEC SQLSET DATABASE EMP = COMPILETIME ?employee.gdb?;IMPORTANTThe file specification that follows the COMPILETIME keyword must always be a hard-coded, quoted string.DECLARING A DATABASEEMBEDDED SQL GUIDE 39When SET DATABASE uses the COMPILETIME clause, but no RUNTIME clause, and does not specify a different database file specification in a subsequent CONNECT statement, the same database file is used both for preprocessing and run time. To specify different preprocessing and runtime databases with SET DATABASE, use both the COMPILETIME andRUNTIME clauses.4Using the RUNTIME clauseWhen a database file is specified for use during preprocessing, SET DATABASE can specify a different database to use at run time by including the RUNTIME keyword and a runtime file specification:EXEC SQLSET DATABASE EMP = COMPILETIME ?employee.gdb?RUNTIME ?employee2.gdb?;The file specification that follows the RUNTIME keyword can be either ahard-coded, quoted string, or a host-language variable. For example, the following C code fragment prompts the user for a database name, and stores the name in a variable that is used later in SET DATABASE:. . .char db_name[125];. . .printf("Enter the desired database name, including node and path):\n");gets(db_name);EXEC SQLSET DATABASE EMP = COMPILETIME ?employee.gdb?RUNTIME : db_name; . . .Note host-language variables in SET DATABASE must be preceded, as always, by a colon.Controlling SET DATABASE scopeBy default, SET DATABASE creates a handle that is global to all modules in an application.A global handle is one that may be referenced in all host-language modules comprising the program. SET DATABASE provides two optional keywords to change the scope of a declaration:g STATIC limits declaration scope to the module containing the SET DATABASE statement. No other program modules can see or use a database handle declared STATIC.CHAPTER 3 WORKING WITH DATABASES40 INTERBASE 6EXTERN notifies gpre that a SET DATABASE statement in a module duplicates a globally-declared database in another module. If the EXTERN keyword is used, then another module must contain the actual SET DATABASE statement, or an error occurs during compilation.The STATIC keyword is used in a multi-module program to restrict database handle access to the single module where it is declared. The following example illustrates the use of the STATIC keyword:EXEC SQLSET DATABASE EMP = STATIC ?employee.gdb?;The EXTERN keyword is used in a multi-module program to signal that SET DATABASE in one module is not an actual declaration, but refers to a declaration made in a different module. Gpre uses this information during preprocessing. Thefollowing example illustrates the use of the EXTERN keyword: EXEC SQLSET DATABASE EMP = EXTERN ?employee.gdb?;If an application contains an EXTERN reference, then when it is used at run time, the actual SET DATABASE declaration must be processed first, and the database connected before other modules can access it.A single SET DATABASE statement can contain either the STATIC or EXTERN keyword, but not both. A scope declaration in SET DATABASE applies to both COMPILETIME and RUNTIME databases.Specifying a connection character setWhen a client application connects to a database, it may have its own character set requirements. The server providing database access to the client does not know about these requirements unless the client specifies them. The client application specifies its character set requirement using the SET NAMES statement before it connects to the database.SET NAMES specifies the character set the server should use when translating data from the database to the client application. Similarly, when the client sends data to the database, the server translates the data from the client?s character set to the database?s default character set (or the character set for an individual column if it differs from the database?s default character set). For example, the followingstatements specify that the client is using the DOS437 character set, then connect to the database:EXEC SQLOPENING A DATABASEEMBEDDED SQL GUIDE 41SET NAMES DOS437;EXEC SQLCONNECT ?europe.gdb? USER ?JAMES? PASSWORD ?U4EEAH?;For more information about character sets, see the Data Definition Guide. For the complete syntax of SET NAMES and CONNECT, see the Language Reference. Opening a database After a database is declared, it must be attached with a CONNECT statement before it can be used. CONNECT:1. Allocates system resources for the database.2. Determines if the database file is local, residing on the same host where the application itself is running, or remote, residing on a different host.3. Opens the database and examines it to make sure it is valid.InterBase provides transparent access to all databases, whether local or remote. If the database structure is invalid, the on-disk structure (ODS) number does not correspond to the one required by InterBase, or if the database is corrupt, InterBase reports an error, and permits no further access. Optionally, CONNECT can be used to specify:4. A user name and password combination that is checked against the server?s security database before allowing the connect to succeed. User names can be up to 31 characters.Passwords are restricted to 8 characters.5. An SQL role name that the user adopts on connection to the database, provided that the user has previously been granted membership in the role. Regardless of role memberships granted, the user belongs to no role unless specified with this ROLE clause.The client can specify at most one role per connection, and cannot switch roles except by reconnecting.6. The size of the database buffer cache to allocate to the application when the default cache size is inappropriate.Using simple CONNECT statementsIn its simplest form, CONNECT requires one or more database parameters, each specifying the name of a database to open. The name of the database can be a: Database handle declared in a previous SET DATABASE statement.CHAPTER 3 WORKING WITH DATABASES42 INTERBASE 61. Host-language variable.2. Hard-coded file name.4Using a database handleIf a program uses SET DATABASE to provide database handles, those handles should be used in subsequent CONNECT statements instead of hard-coded names. For example, . . .EXEC SQLSET DATABASE DB1 = ?employee.gdb?;EXEC SQLSET DATABASE DB2 = ?employee2.gdb?;EXEC SQLCONNECT DB1;EXEC SQLCONNECT DB2;. . .There are several advantages to using a database handle with CONNECT:1. Long file specifications can be replaced by shorter, mnemonic handles.2. Handles can be used to qualify table names in multi-database transactions. DSQL applications do not support multi-database transactions.3. Handles can be reassigned to other databases as needed.4. The number of database cache buffers can be specified as an additional CONNECT parameter.For more information about setting the number of databas e cache buffers, see “Setting database cache buffers” on page 47. 4Using strings or host-language variables Instead of using a database handle, CONNECT can use a database name supplied at run time. The database name can be supplied as either a host-language variable or a hard-coded, quoted string.The following C code demonstrates how a program accessing only a single database might implement CONNECT using a file name solicited from a user at run time:. . .char fname[125];. . .printf(?Enter the desired database name, including nodeand path):\n?);OPENING A DATABASEEMBEDDED SQL GUIDE 43gets(fname);. . .EXEC SQLCONNECT :fname;. . .TipThis technique is especially useful for programs that are designed to work with many identically structured databases, one at a time, such as CAD/CAM or architectural databases.MULTIPLE DATABASE IMPLEMENTATIONTo use a database specified by the user as a host-language variable in a CONNECT statement in multi-database programs, follow these steps:1. Declare a database handle using the following SET DATABASE syntax:。

数据库安全中英文对照外文翻译文献

中英文对照外文翻译文献(文档含英文原文和中文翻译)Database Security in a Web Environment IntroductionDatabases have been common in government departments and commercial enterprises for many years. Today, databases in any organization are increasingly opened up to a multiplicity of suppliers, customers, partners and employees - an idea that would have been unheard of a few years ago. Numerous applications and their associated data are now accessed by a variety of users requiring different levels of access via manifold devices and channels – often simultaneously. For example:• Online banks allow customers to perform a variety of banking operations - via the Internet and over the telephone – whilst maintaining the privacy of account data.• E-Commerce merchants and their Service Providers must store customer, order and payment data on their merchant server - and keep it secure.• HR departments allow employees to update their personal information –whilst protecting certain management information from unauthorized access.• The medical profession must protect the confidentiality of patient data –whilst allowing essential access for treatment.• Online brokerages need to be able to provide large numbers of simultaneous users with up-to-date and accurate financial information.This complex landscape leads to many new demands upon system security. The global growth of complex web-based infrastructures is driving a need for security solutions that provide mechanisms to segregate environments; perform integrity checking and maintenance; enable strong authentication andnon-repudiation; and provide for confidentiality. In turn, this necessitates comprehensive business and technical risk assessment to identify the threats,vulnerabilities and impacts, and from this define a security policy. This leads to security definitions throughout the infrastructure - operating system, database management system, middleware and network.Financial, personal and medical information systems and some areas of government have strict requirements for security and privacy. Inappropriate disclosure of sensitive information to the wrong parties can have severe social, legal and regulatory consequences. Failure to address the basics can result in substantial direct and consequential financial losses - witness the fraud losses through the compromise of several million credit card numbers in merchants’ databases [Occf], plus associated damage to brand-image and loss of consumer confidence.This article discusses some of the main issues in database and web server security, and also considers important architecture and design issues.A Simple ModelAt the simplest level, a web server system consists of front-end software and back-end databases with interface software linking the two. Normally, the front-end software will consist of server software and the network server operating system, and the back-end database will be a relational orobject-oriented database fulfilling a variety of functions, including recording transactions, maintaining accounts and inventory. The interface software typically consists of Common Gateway Interface (CGI) scripts used to receive information from forms on web sites to perform online searches and to update the database.Depending on the infrastructure, middleware may be present; in addition, security management subsystems (with session and user databases) that address the web server’s and related applications’ requirements for authentication, accesscontrol and authorization may be present. Communications between this subsystem and either the web server, middleware or database are via application program interfaces (APIs)..This simple model is depicted in Figure 1.Security can be provided by the following components:• Web server.• Middleware.• Operating system.. Figure 1: A Simple Model.• Database and Database Management System.• Security management subsystem.The security of such a system addressesAspects of authenticity, integrity and confidentiality and is dependent on the security of the individual components and their interactions. Some of the most common vulnerabilities arise from poor configuration, inadequate change control procedures and poor administration. However, even if these areas are properlyaddressed, vulnerabilities still arise. The appropriate combination of people, technology and processes holds the key to providing the required physical and logical security. Attention should additionally be paid to the security aspects of planning, architecture, design and implementation.In the following sections, we consider some of the main security issues associated with databases, database management systems, operating systems and web servers, as well as important architecture and design issues. Our treatment seeks only to outline the main issues and the interested reader should refer to the references for a more detailed description.Database SecurityDatabase management systems normally run on top of an operating system and provide the security associated with a database. Typical operating system security features include memory and file protection, resource access control and user authentication. Memory protection prevents the memory of one program interfering with that of another and limits access and use of the objects employing techniques such as memory segmentation. The operating system also protects access to other objects (such as instructions, input and output devices, files and passwords) by checking access with reference to access control lists. Security mechanisms in common operating systems vary tremendously and, for those that are lacking, there exists special-purpose security software that can be integrated with the existing environment. However, this can be an expensive, time-consuming task and integration difficulties may also adversely impact application behaviors.Most database management systems consist of a number of modules - including database querying and database and file management - along with authorization, concurrent access and database description tables. Thesemanagement systems also use a variety of languages: a data definition language supports the logical definition of the database; developers use a data manipulation language; and a query language is used by non-specialist end-users.Database management systems have many of the same security requirements as operating systems, but there are significant differences since the former are particularly susceptible to the threat of improper disclosure, modification of information and also denial of service. Some of the most important security requirements for database management systems are: • Multi-Level Access Control.• Confidentiality.• Reliability.• Integrity.• Recovery.These requirements, along with security models, are considered in the following sections.Multi-Level Access ControlIn a multi-application and multi-user environment, administrators, auditors, developers, managers and users – collectively called subjects - need access to database objects, such as tables, fields or records. Access control restricts the operations available to a subject with respect to particular objects and is enforced by the database management system. Mandatory access controls require that each controlled object in the database must be labeled with a security level, whereas discretionary access controls may be applied at the choice of a subject.Access control in database management systems is more complicated than in operating systems since, in the latter, all objects are unrelated whereas in a database the converse is true. Databases are also required to make accessdecisions based on a finer degree of subject and object granularity. In multi-level systems, access control can be enforced by the use of views - filtered subsets of the database - containing the precise information that a subject is authorized to see.A general principle of access control is that a subject with high level security should not be able to write to a lower level object, and this poses a problem for database management systems that must read all database objects and write new objects. One solution to this problem is to use a trusted database management system.ConfidentialitySome databases will inevitably contain what is considered confidential data. For example, it could be inherently sensitive or its source may be sensitive, or it may belong to a sensitive table, thus making it difficult to determine what is actually confidential. Disclosure is also difficult to define, as it can be direct, indirect, involve the disclosure of bounds or even mere existence.An inference problem exists in database management systems whereby users can infer sensitive information from relatively insensitive queries. A trivial example is a request for information about the average salary of an employee and the number of employees turns out to be just one, thus revealing the employee’s salary. However, much more sophisticated statistical inference attacks can also be mounted. This highlights the fact that, although the data itself may be properly controlled, confidential information may still leak out.Controls can take several forms: not divulging sensitive information to unauthorized parties (which depends on the respective subject and object security levels), logging what each user knows or masking response data. The first control can be implemented fairly easily, the second quickly becomesunmanageable for a large number of users and the third leads to imprecise responses, and also exemplifies the trade-off between precision and security. Polyinstantiation refers to multiple instances of a data object existing in the database and it can provide a partial solution to the inference problem whereby different data values are supplied, depending on the security level, in response to the same query. However, this makes consistency management more difficult.Another issue that arises is when the security level of an aggregate amount is different to that of its elements (a problem commonly referred to as aggregation). This can be addressed by defining appropriate access control using views.Reliability, Integrity and RecoveryArguably, the most important requirements for databases are to ensure that the database presents consistent information to queries and can recover from any failures. An important aspect of consistency is that transactions execute atomically; that is, they either execute completely or not at all.Concurrency control addresses the problem of allowing simultaneous programs access to a shared database, while avoiding incorrect behavior or interference. It is normally addressed by a scheduler that uses locking techniques to ensure that the transactions are serial sable and independent. A common technique used in commercial products is two-phase locking (or variations thereof) in which the database management system controls when transactions obtain and release their locks according to whether or not transaction processing has been completed. In a first phase, the database management system collects the necessary data for the update: in a second phase, it updates the database. This means that the database can recover from incomplete transactions by repeatingeither of the appropriate phases. This technique can also be used in a distributed database system using a distributed scheduler arrangement.System failures can arise from the operating system and may result in corrupted storage. The main copy of the database is used for recovery from failures and communicates with a cached version that is used as the working version. In association with the logs, this allows the database to recover to a very specific point in the event of a system failure, either by removing the effects of incomplete transactions or applying the effects of completed transactions. Instead of having to recover the entire database after a failure, recovery can be made more efficient by the use of check pointing. It is used during normal operations to write additional updated information - such as logs, before-images of incomplete transactions, after-images of completed transactions - to the main database which reduces the amount of work needed for recovery. Recovery from failures in distributed systems is more complicated, since a single logical action is executed at different physical sites and the prospect of partial failure arises.Logical integrity, at field level and for the entire database, is addressed by the use of monitors to check important items such as input ranges, states and transitions. Error-correcting and error-detecting codes are also used.Security ModelsVarious security models exist that address different aspects of security in operating systems and database management systems. For example, theBell-LaPadula model defines security in terms of mandatory access control and addresses confidentiality only. The Bell LaPadula models, and other models including the Biba model for integrity, are described more fully in [Cast95] and [Pfle89]. These models are implementation-independent and provide a powerfulinsight into the properties of secure systems, lead to design policies and principles, and some form the basis for security evaluation criteria.Web Server SecurityWeb servers are now one of the most common interfaces between users and back-end databases, and as such, their security becomes increasingly important. Exploitation of vulnerabilities in the web server can lead to unforeseen attacks on middleware and backend databases, bypassing any controls that may be in place. In this section, we focus on common web server vulnerabilities and how the authentication requirements of web servers and databases are met.In general, a web server platform should not be shared with other applications and should be the only machine allowed to access the database. Using a firewall can provide additional security - either between the web server and users or between the web server and back-end database - and often the web server is placed on a de-militarized zone (DMZ) of a firewall. While firewalls can be used to block certain incoming connections, they must allow HTTP (and HTTPS) connections through to the web server, and so attacks can still be launched via the ports associated with these connections.VulnerabilitiesVulnerabilities appear on a weekly basis and, here, we prefer to focus on some general issues rather than specific attacks. Common web server vulnerabilities include:• No policy exists.• The default configuration is on.• Reusable passwords appear in clear.• Unnecessary ports available for network services are not disabled.• New security holes are not tracked. Even if they are, well-known vulnerabilities are not always fixed as the source code patches are not applied by system administrator and old programs are not re-compiled or removed.• Security tools are not used to scan the network for weaknesses and changes or to detect intrusions.• Faulty and buggy software - for example, buffer overflow and stack smashingAttacks• Automatic directory listings - this is of particular concern for the interface software directories.• Server root files are generally visible or accessible.• Lack of logs and bac kups.• File access is often not explicitly configured by the system administrator according to the security policy. This applies to configuration, client, administration and log files, administration programs, and CGI program sources and executables. CGI scripts allow dynamic web pages and make program development (in, for example, Perl) easy and rapid. However, their successful exploitation may allow execution of malicious programs, launching ofdenial-of-service attacks and, ultimately, privilege escalation on a server.Web Server and Database AuthenticationWhile user, browser and web server authentication are relatively well understood [Garf97], [Ghos98] and [Tree98], the introduction of additional components, such as databases and middleware, raise a number of authentication issues. There are a variety of options for authentication in a simple model (Figure 1). Firstly, both the web server and database management system can individually authenticate a user. This option requires the user to authenticatetwice which may be unacceptable in certain applications, although a singlesign-on device (which aims to manage authentication in a user-transparent way) may help. Secondly, a common approach is for the database to automatically grant user access based on web server authentication. However, this option should only be used for accessing publicly available information. Finally, the database may grant user access employing the web server authentication credentials as a basis for its own user authentication, using security management subsystems (Figure 1). We consider this last option in more detail.Web-based communications use the stateless HTTP protocol with the implication that state, and hence authentication, is not preserved when browsing successive web pages. Cookies, or files placed on user’s machine by a web server, were developed as a means of addressing this issue and are often used to provide authentication. However, after initial authentication, there is typically no re authentication per page in the same realm, only the use of unencrypted cookies (sometimes in association with IP addresses). This approach provides limited security as both cookies and IP addresses can be tampered with or spoofed.A stronger authentication method, commonly used by commercial implementations, uses digitally signed cookies. This allows additional systems, such as databases, to use digitally signed cookie data, including a session ID, as a basis for authentication. When a user has been authenticated by a web server (using a password, for example), a session ID is assigned and is stored in a security management subsystem database. When a user subsequently requests information from a database, the database receives a copy of the session ID, the security management subsystem checks this session ID against its local copy and, if authentication is successful, user access is granted to the database.The session ID is typically transmitted in the clear between the web server and database, but may be protected by SSL or even by physical security measures. The communications between the browser and web servers, and the web servers and security management subsystem (and its databases), are normally protected by SSL and use a web server security API that is used to digitally sign and verify browser cookies. The communications between the back-end databases and security management subsystem (and its databases) are also normally protected by SSL and use a database security API that verifies session Ids originating from the database and provides additional user authorization credentials. The web server security API is generally proprietary while, for the database security API, many vendors have adopted standards such as the Generic Security Services API (GSS-API) or CORBA [RFC2078] and [Corba].Architecture and DesignSecurity requirements for designing, building and implementing databases are important so that the systems, as part of the overall infrastructure, meet their requirements in actual operation. The various security models provide an important insight into the design requirements for databases and their management systems.Secure Database Management System ArchitecturesIn multi-level database management systems, a variety of architectures are possible: trusted subject, integrity locked, kernels and replicated. Trusted subject is used by most of the leading database management system vendors and can be integrated in existing products. Basically, the trusted subject architecture allows users to access a database via an un trusted front-end, a trusted database management system and trusted operating system. The operating systemprovides physical access to the database and the database management system provides multilevel object protection.The other architectures - integrity locked, kernels and replicated - all vary in detail, but they use a trusted front-end and an un trusted database management system. For details of these architectures and research prototypes, the reader is referred to [Cast95]. Different architectures are suited to different environments: for example, the trusted subject architecture is less integrated with the underlying operating system and is best suited when a trusted path can be assured between applications and the database management system.Secure Database Management System DesignAs discussed above, there are several fundamental differences between operating system and database management system design, including object granularity, multiple data types, data correlations and multi-level transactions. Other differences include the fact that database management systems include both physical and logical objects and that the database lifecycle is normally longer.These differences must be reflected in the design requirements which include:• Access, flow and infer ence controls.• Access granularity and modes.• Dynamic authorization.• Multi-level protection.• Polyinstantiation.• Auditing.• Performance.These requirements should be considered alongside basic information integrity principles, such as:• Well-formed transactions - to ensure that transactions are correct and consistent.• Continuity of operation - to ensure that data can be properly recovered, depending on the extent of a disaster.• Authorization and role management – to ensure that distinct roles are defined and users are authorized.• Authenticated users - to ensure that users are authenticated.• Least privilege - to ensure that users have the minimal privilege necessary to perform their tasks.• Separation of duties - to ensure that no single individual has access to critical data.• Delegation of authority - to ensure that the database management system policies are flexible enough to meet the organization’s requirements.Of course, some of these requirements and principles are not met by the database management system, but by the operating system and also by organizational and procedural measures.Database Design MethodologyVarious approaches to design exist, but most contain the same main stages. The principle aim of a design methodology is to provide a robust, verifiable design process and also to separate policies from how policies are actually implemented. An important requirement during any design process is that different design aspects can be merged and this equally applies to security.A preliminary analysis should be conducted that addresses the system risks, environment, existing products and performance. Requirements should then beanalyzed with respect to the results of a risk assessment. Security policies should be developed that include specification of granularity, privileges and authority.These policies and requirements form the input to the conceptual design that concentrates on subjects, objects and access modes without considering implementation details. Its purpose is to express information and process flows in a complete and consistent way.The logical design takes into account the operating system and database management system that will be used and which of the security requirements can be provided by which mechanisms. The physical design considers the actual physical realization of the logical design and, indeed, may result in a revision of the conceptual and logical phases due to physical constraints.Security AssuranceOnce a product has been developed, its security assurance can be assessed by a number of methods including formal verification, validation, penetration testing and certification. For example, if a database is to be certified as TCSEC Class B1, then it must implement the Bell-LaPadula mandatory access control model in which each controlled object in the database must be labeled with a security level.Most of these methods can be costly and lengthy to perform and are typically specific to particular hardware and software configurations. However, the international Common Criteria certification scheme provides the added benefit of a mutual recognition arrangement, thus avoiding the prospect of multiple certifications in different countries.ConclusionThis article has considered some of the security principles that are associated with databases and how these apply in a web based environment. Ithas also focused on important architecture and design principles. These principles have focused mainly on the prevention, assurance and recovery aspects, but other aspects, such as detection, are equally important in formulating a total information protection strategy. For example, host-based intrusion detection systems as well as a robust and tested set of business recovery procedures should be considered.Any fit-for-purpose, secure e-business infrastructure should address all the above aspects: prevention, assurance, detection and recovery. Certain industries are now starting to specify their own set of global, secure e-business requirements. International card payment associations have recently started to require minimum information security standards from electronic commerce merchants handling credit card data, to help manage fraud losses and associated impacts such as brand-image damage and loss of consumer confidence.网络环境下的数据库安全简介数据库在政府部门和商业机构得到普遍应用已经很多年了。

关于sql的参考文献

关于sql的参考文献SQL（Structured Query Language）是一种用于管理和操作关系型数据库的标准化语言。

在学习和使用SQL时，参考文献是非常重要的资源，它们可以提供详细的指导和深入的理解。

以下是一些关于SQL的参考文献，它们涵盖了不同的主题和难度级别，可以帮助你深入学习和掌握SQL。

1. "SQL Cookbook" by Anthony Molinaro 这本书提供了大量的SQL问题和解决方案，涵盖了各种常见的数据库操作和查询场景。

它适合那些希望通过实际问题来学习SQL的人。

2. "SQL in 10 Minutes a Day" by Ben Forta 这本书适合初学者，它以简洁明了的方式介绍了SQL的基本概念和语法。

通过逐步构建知识，读者可以快速入门SQL。

3. "Learning SQL" by Alan Beaulieu 这本书适合那些希望深入学习SQL的人。

它涵盖了SQL的基础知识和高级概念，包括数据库设计、查询优化和数据分析等方面。

4. "SQL Performance Explained" by Markus Winand 这本书专注于SQL性能优化，它探讨了如何编写高效的SQL查询和设计高性能的数据库架构。

对于那些希望提高SQL查询性能的人来说，这是一本非常有价值的参考书。

5. "SQL Antipatterns: Avoiding the Pitfalls of Database Programming" by Bill Karwin 这本书介绍了一些常见的SQL反模式和错误，以及如何避免它们。

通过学习这些反模式，读者可以提高自己编写高质量SQL代码的能力。

6. "The Art of SQL" by Stephane Faroult and Peter Robson 这本书深入探讨了SQL的内部工作原理和优化技巧。

sqlserver数据库介绍的书籍 -回复

sqlserver数据库介绍的书籍-回复SQL Server数据库介绍的书籍SQL Server是一种关系型数据库管理系统，由微软公司开发和提供支持。

它具有广泛的应用领域，从小型企业到大型企业都可以使用它来存储和处理数据。

对于想要学习SQL Server数据库的人来说，书籍是一个非常有用的资源。

在这篇文章中，我将介绍一些SQL Server数据库介绍的书籍，并为您逐步解释它们的内容。

1. "SQL Server 2017 Bible" by Adam Jorgensen, Stacia Varga, Denny Cherry, and Joseph D'Antoni.这本书是关于SQL Server 2017版本的指南。

它详细介绍了SQL Server的各个方面，包括数据库管理、查询编写、性能调优、安全性以及高可用性和灾难恢复。

这本书非常适合初学者和有经验的SQL Server用户，可以帮助读者了解SQL Server的基本概念和功能。

2. "Microsoft SQL Server 2019: A Beginner's Guide" by Dusan Petkovic.这本书适用于初学者，它提供了一个全面的介绍，帮助读者了解SQL Server 2019的基本概念和功能。

书中包含大量的示例和练习，以加深对SQL Server的理解。

读者可以学习如何创建数据库、执行查询以及管理和维护SQL Server的技巧。

3. "Pro SQL Server Internals" by Dmitri Korotkevitch.这本书适用于那些希望深入了解SQL Server内部工作原理的读者。

它涵盖了SQL Server的存储引擎、查询优化、并发控制和事务管理等方面。

作者提供了详细的解释和示例，以帮助读者理解SQL Server的内部工作原理，并优化数据库性能。

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SQL数据库英文文献及翻译The fact that you are reading a book on SQL indicates that you, somehow, need to interact with databases. SQL is a language used to do just this, so before looking at SQL itself, it is important that you understand some basic concepts about databases and database technologies.Whether you are aware of it or not, you use databases all the time. Each time you select a name from your email address book, you are using a database. If you conduct a search on an Internet search site, you are using a database. When you log into your network at work, you are validating your name and password against a database. Even when you use your ATM card at a cash machine, you are using databases for PIN number verification and balance checking.But even though we all use databases all the time, there remains much confusion over what exactly a database is. This is especially true because different people use the same database terms to mean different things. Therefore, a good place to start our study is with a list and explanation of the most important database terms.Reviewing Basic Concepts What follows is a very brief overview of some basic database concepts. It is intended to either jolt your memory if you already have some database experience, or to provide you with the absolute basics, if you are new to databases. Understanding databases is an important part of mastering SQL, and you might want to find a good book on database fundamentals to brush up on the subject if needed.What Is a Database?The term database is used in many organized fashion. The simplest way to think of it is to imagine a database as a filing cabinet. The filing cabinet is simply a physical location to store data, regardless of what that data is or how it is organizedDatabase A container (usually a file or set of files) to store organized data.Misuse Causes ConfusionPeople often use the term database to refer to the database software they are running. This is incorrect, and it is a source of much confusion. Database software is actually called the Database Management System (or DBMS). The database is the container created and manipulated via the DBMS. A database might be a file stored on a hard drive, but it might not. And for the most part this is not even significant as you never access a database directly anyway; you always use the DBMS and it accesses the database for you.TablesWhen you store information in your filing cabinet you don't just toss it in a drawer. Rather, you create files within the filing cabinet, and then you file related data in specific files.In the database world, that file is called a table. A table is a structured file that can store data of a specific type. A table might contain a list of customers, a product catalog, or any other list of information.Table A structured list of data of a specific type.The key here is that the data stored in the table is one type of data or one list. You would never store a list of customers and a list of orders in the same database table. Doing so would make subsequent retrieval and access difficult. Rather, you'd create two tables, one for each list.Every table in a database has a name that identifies it. That name is always unique—meaning no other table in that database can have the same name.Table Names What makes a table name unique is actually a combination of several things including the database name and table name. Some databases also use the name of the database owner as part of the unique name. This means that while you cannot use the same table nametwice in the same database, you definitely can reuse table names in different databases.Tables have characteristics and properties that define how data is stored in them. These include information about what data may be stored, how it is broken up, how individual pieces of information are named, and much more. This set of information that describes a table is known as a schema, and schema are used to describe specific tables within a database, as well as entire databases (and the relationship between tables in them, if any).Schema Information about database and table layout and properties.Columns and DatatypesTables are made up of columns. A column contains a particular piece of information within a table. Column A single field in a table. All tables are made up of one or more columns.The best way to understand this is to envision database tables as grids, somewhat like spreadsheets. Each column in the grid contains a particular piece of information. In a customer table, for example, one column contains the customer number, another contains the customer name, and the address, city, state, and zip are all stored in their own columnsBreaking Up DataIt is extremely important to break data into multiple columns correctly. For example, city, state, and zip should always be separate columns. By breaking these out, it becomes possible to sort or filter data by specific columns (for example, to find all customers in a particular state or in a particular city). If city and state are combined into one column, it would be extremely difficult to sort or filter by state.1657Each column in a database has an associated datatype. A datatype defines what type of data the column can contain. For example, if the column is to contain a number (perhaps the number of items in an order), the datatype would be a numeric datatype. If the column were to contain dates, text, notes, currency amounts, and so on, the appropriate datatype would be used to specify this. DatatypeA type of allowed data. Every table column has an associated datatype that restricts (or allows) specific data in that column.Datatypes restrict the type of data that can be stored in a column (for example, preventing the entry of alphabetical characters into a numeric field). Datatypes also help sort data correctly, and play an important role in optimizing disk usage. As such, special attention must be given to picking the right datatype when tables are created.Datatype CompatibilityDatatypes and their names are one of the primary sources of SQL incompatibility. While most basic datatypes are supported consistently, many more advanced datatypes are not. And worse, occasionally you'll find that the same datatype is referred to by Data in a table is stored in rows; each record saved is stored in its own row. Again, envisioning a table as a spreadsheet style grid, the vertical columns in the grid are the table columns, and the horizontal rows are the table rows. For example, a customers table might store one customer per row. The number of rows in the table is the number of records in it.Row A record in a table.Records or Rows?You may hear users refer to database records when referring to rows. For the most part, the two terms are used interchangeably, but row is technically the correct term.Primary KeysEvery row in a table should have some column (or set of columns) that uniquely identifies it. A table containing customers might use a customer number column for this purpose, whereas a table containing orders might use the order ID. An employee list table might use an employee ID or the employee social security number column.This column (or set of columns) that uniquely identifies each row in a table is called a primary key. The primary key is used to refer to a specific row. Without a primary key, updating or deleting specific rows in a table becomes extremely difficult as there is no guaranteed safe way to refer to just the rows to be affected.Always Define Primary Keys Although primary keys are not actually required, most database designers ensure that every table they create has a primary key so that future data manipulation is possible and manageable.Any column in a table can be established as the primary key, as long as it meets the following conditions:•No two rows can have the same primary key value.•Every row must have a primary key value (primary key columns may not allow NULL values). •Values in primary key columns can never be modified or updated.•Primary key values can never be reused. (If a row is deleted from the table, its primary key may not be assigned to any new rows in the future.)What Is SQL?SQL (pronounced as the letters S-Q-L or as sequel) is an abbreviation for Structured Query Language. SQL is a language designed specifically for communicating with databases.Unlike other languages (spoken languages like English, or programming languages like Java or Visual Basic), SQL is made up of very few words. This is deliberate. SQL is designed to do one thing and do it well—provide you with a simple and efficient way to read and write data from a database.Primary keys are usually defined on a single column within a table. But this is not required, and multiple columns may be used together as a primary key. When multiple columns are used, the rules listed above must apply to all columns that make up the primary key, and the values of all columns together must be unique (individual columns need not have unique values).。