数据库优化服务(外文翻译)
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。
数据库设计外文翻译
外文翻译：索引原文来源：Thomas Kyte．Expert Oracle Database Architecture ．2nd Edition．译文正文：什么情况下使用B*树索引?我并不盲目地相信“法则”（任何法则都有例外），对于什么时候该用B*索引，我没有经验可以告诉你。
为了证明为什么这个方面我无法提供任何经验，下面给出两种等效作法：•使用B*树索引，如果你想通过索引的方式去获得表中所占比例很小的那些行。
•使用B *树索引，如果你要处理的表和索引许多可以代替表中使用的行。
这些规则似乎提供相互矛盾的意见，但在现实中，他们不是这样的，他们只是涉及两个极为不同的情况。
有两种方式使用上述意见给予索引：•作为获取表中某些行的手段。
你将读取索引去获得表中的某一行。
在这里你想获得表中所占比例很小的行。
•作为获取查询结果的手段。
这个索引包含足够信息来回复整个查询，我们将不用去查询全表。
这个索引将作为该表的一个瘦版本。
还有其他方式—例如，我们使用索引去检索表的所有行，包括那些没有建索引的列。
这似乎违背了刚提出的两个规则。
这种方式获得将是一个真正的交互式应用程序。
该应用中，其中你将获取其中的某些行，并展示它们，等等。
你想获取的是针对初始响应时间的查询优化，而不是针对整个查询吞吐量的。
在第一种情况（也就是你想通过索引获得表中一小部分的行）预示着如果你有一个表T （使用与早些时候使用过的相一致的表T）,然后你获得一个像这样查询的执行计划：ops$tkyte%ORA11GR2> set autotrace traceonly explainops$tkyte%ORA11GR2> select owner, status2 from t3 where owner = USER;Execution Plan----------------------------------------------------------Plan hash value: 1049179052------------------------------------------------------------------| Id | Operation | Name | Rows | Bytes |------------------------------------------------------------------| 0 | SELECT STATEMENT | | 2120 | 23320 || 1 | TABLE ACCESS BY INDEX ROWID |T | 2120 | 23320 || *2 | INDEX RANGE SCAN | DESC_T_IDX | 8 | |------------------------------------------------------------------Predicate Information (identified by operation id):---------------------------------------------------2 - access(SYS_OP_DESCEND("OWNER")=SYS_OP_DESCEND(USER@!))filter(SYS_OP_UNDESCEND(SYS_OP_DESCEND("OWNER"))=USER@!)你应该访问到该表的一小部分。
外文翻译---数据库管理
英文资料翻译资料出处：From /china/ database英文原文：Database ManagementDatabase (sometimes spelled database) is also called an electronic database, referring to any collections 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. Database 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 the these files may be broken down into records, each of which consists of one or more 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 aggregates of data.Database records and files must be organized to allow retrieval of the information. Early system were arranged sequentially (i.e., alphabetically, numerically, or chronologically); the development of direct-access storage devices made possible random access to data via indexes. Queries are the main way users retrieve database information. Typically the user provides a string of characters, and the computer searches the database for a corresponding sequence and provides the source materials in which those characters appear. A user can request, for example, all records in which the content of the field for a person’s last name is the word Smith.The many users of a large database must be able to manipulate the information within it quickly at any given time. Moreover, large business and other organizations tend to build up many independent files containing related and even overlapping data, and their data, processing activities often require the linking of data from several files.Several different types of database management systems have been developed to support these requirements: flat, hierarchical, network, relational, and object-oriented.In flat databases, records are organized according to a simple list of entities; many simple databases for personal computers are flat in structure. The records in hierarchical databases are organized in a treelike structure, with each level of records branching off into a set of smaller categories. Unlike hierarchical databases, which provide single links between sets of records at different levels, network databases create multiple linkages between sets by placing links, or pointers, to one set of records in another; the speed and versatility of network databases have led to their wide use in business. Relational databases are used where associations among files or records cannot be expressed by links; a simple flat list becomes one table, or “relation”, and multiple relations can be mathematically associated to yield desired information. Object-oriented databases store and manipulate more complex data structures, called “objects”, which are organized into hierarchical classes that may inherit properties from classes higher in the chain; this database structure is the most flexible and adaptable.The information in many databases consists of natural-language texts of documents; number-oriented database primarily contain information such as statistics, tables, financial data, and raw scientific and technical data. Small databases can be maintained on personal-computer systems and may be used by individuals at home. These and larger databases have become increasingly important in business life. Typical commercial applications include airline reservations, production management, medical records in hospitals, and legal records of insurance companies. The largest databases are usually maintained by governmental agencies, business organizations, and universities. These databases may contain texts of such materials as catalogs of various kinds. Reference databases contain bibliographies or indexes that serve as guides to the location of information in books, periodicals, and other published literature. Thousands of these publicly accessible databases now exist, covering topics ranging from law, medicine, and engineering to news and current events, games, classified advertisements, and instructional courses. Professionals such as scientists,doctors, lawyers, financial analysts, stockbrokers, and researchers of all types increasingly rely on these databases for quick, selective access to large volumes of information.一、DBMS Structuring TechniquesSequential, direct, and other file processing approaches are used to organize and structure data in single files. But a DBMS is able to integrate data elements from several files to answer specific user inquiries for information. That is, the DBMS is able to structure and tie together the logically related data from several large files.Logical Structures. Identifying these logical relationships is a job of the data administrator. A data definition language is used for this purpose. The DBMS may then employ one of the following logical structuring techniques during storage access, and retrieval operations.List structures. In this logical approach, records are linked together by the use of pointers. A pointer is a data item in one record that identifies the storage location of another logically related record. Records in a customer master file, for example, will contain the name and address of each customer, and each record in this file is identified by an account number. During an accounting period, a customer may buy a number of items on different days. Thus, the company may maintain an invoice file to reflect these transactions. A list structure could be used in this situation to show the unpaid invoices at any given time. Each record in the customer in the invoice file. This invoice record, in turn, would be linked to later invoices for the customer. The last invoice in the chain would be identified by the use of a special character as a pointer.Hierarchical (tree) structures. In this logical approach, data units are structured in multiple levels that graphically resemble an “upside down”tree with the root at the top and the branches formed below. There’s a superior-subordinate relationship in a hierarchical (tree) structure. Below the single-root data component are subordinate elements or nodes, each of which, in turn, “own”one or more other elements (or none). Each element or branch in this structure below the root has only a single owner. Thus, a customer owns an invoice, and the invoice has subordinate items. Thebranches in a tree structure are not connected.Network Structures. Unlike the tree approach, which does not permit the connection of branches, the network structure permits the connection of the nodes in a multidirectional manner. Thus, each node may have several owners and may, in turn, own any number of other data units. Data management software permits the extraction of the needed information from such a structure by beginning with any record in a file.Relational structures. A relational structure is made up of many tables. The data are stored in the form of “relations”in these tables. For example, relation tables could be established to link a college course with the instructor of the course, and with the location of the class.To find the name of the instructor and the location of the English class, the course/instructor relation is searched to get the name (“Fitt”), and the course/locati on relation is a relatively new database structuring approach that’s expected to be widely implemented in the future.Physical Structures. People visualize or structure data in logical ways for their own purposes. Thus, records R1 and R2 may always be logically linked and processed in sequence in one particular application. However, in a computer system it’s quite possible that these records that are logically contiguous in one application are not physically stored together. Rather, the physical structure of the records in media and hardware may depend not only on the I/O and storage devices and techniques used, but also on the different logical relationships that users may assign to the data found in R1and R2. For example, R1 and R2 may be records of credit customers who have shipments send to the same block in the same city every 2 weeks. From the shipping department manager’s perspective, then, R1 and R2 are sequential entries on a geographically organized shipping report. But in the A/R application, the customers represented by R1 and R2 may be identified, and their accounts may be processed, according to their account numbers which are widely separated. In short, then, the physical location of the stored records in many computer-based information systems is invisible to users.二、Database Management Features of OracleOracle includes many features that make the database easier to manage. We’ve divided the discussion in this section into three categories: Oracle Enterprise Manager, add-on packs, backup and recovery.1.Oracle Enterprise ManagerAs part of every Database Server, Oracle provides the Oracle Enterprise Manager (EM), a database management tool framework with a graphical interface used to manage database users, instances, and features (such as replication) that can provide additional information about the Oracle environment.Prior to the Oracle8i database, the EM software had to be installed on Windows 95/98 or NT-based systems and each repository could be accessed by only a single database manager at a time. Now you can use EM from a browser or load it onto Windows 95/98/2000 or NT-based systems. Multiple database administrators can access the EM repository at the same time. In the EM repository for Oracle9i, the super administrator can define services that should be displayed on other administrators’consoles, and management regions can be set up.2. Add-on packsSeveral optional add-on packs are available for Oracle, as described in the following sections. In addition to these database-management packs, management packs are available for Oracle Applications and for SAP R/3.(1) standard Management PackThe Standard Management Pack for Oracle provides tools for the management of small Oracle databases (e.g., Oracle Server/Standard Edition). Features include support for performance monitoring of database contention, I/O, load, memory use and instance metrics, session analysis, index tuning, and change investigation and tracking.(2) Diagnostics PackYou can use the Diagnostic Pack to monitor, diagnose, and maintain the health of Enterprise Edition databases, operating systems, and applications. With both historical and real-time analysis, you can automatically avoid problems before theyoccur. The pack also provides capacity planning features that help you plan and track future system-resource requirements.(3)Tuning PackWith the Tuning Pack, you can optimise system performance by identifying and tuning Enterprise Edition databases and application bottlenecks such as inefficient SQL, poor data design, and the improper use of system resources. The pack can proactively discover tuning opportunities and automatically generate the analysis and required changes to tune the systems.(4) Change Management PackThe Change Management Pack helps eliminate errors and loss of data when upgrading Enterprise Edition databases to support new applications. It impact and complex dependencies associated with application changes and automatically perform database upgrades. Users can initiate changes with easy-to-use wizards that teach the systematic steps necessary to upgrade.(5) AvailabilityOracle Enterprise Manager can be used for managing Oracle Standard Edition and/or Enterprise Edition. Additional functionality is provided by separate Diagnostics, Tuning, and Change Management Packs.3. Backup and RecoveryAs every database administrator knows, backing up a database is a rather mundane but necessary task. An improper backup makes recovery difficult, if not impossible. Unfortunately, people often realize the extreme importance of this everyday task only when it is too late –usually after losing business-critical data due to a failure of a related system.The following sections describe some products and techniques for performing database backup operations.(1) Recovery ManagerTypical backups include complete database backups (the most common type), database backups, control file backups, and recovery of the database. Previously,Oracle’s Enterprise Backup Utility (EBU) provided a similar solution on some platforms. However, RMAN, with its Recovery Catalog stored in an Oracle database, provides a much more complete solution. RMAN can automatically locate, back up, restore, and recover databases, control files, and archived redo logs. RMAN for Oracle9i can restart backups and restores and implement recovery window policies when backups expire. The Oracle Enterprise Manager Backup Manager provides a GUI-based interface to RMAN.(2) Incremental backup and recoveryRMAN can perform incremental backups of Enterprise Edition databases. Incremental backups back up only the blocks modified since the last backup of a datafile, tablespace, or database; thus, they’re smaller and faster than complete backups. RMAN can also perform point-in-time recovery, which allows the recovery of data until just prior to a undesirable event.(3) Legato Storage ManagerVarious media-management software vendors support RMAN. Oracle bundles Legato Storage Manager with Oracle to provide media-management services, including the tracking of tape volumes, for up to four devices. RMAN interfaces automatically with the media-management software to request the mounting of tapes as needed for backup and recovery operations.(4)AvailabilityWhile basic recovery facilities are available for both Oracle Standard Edition and Enterprise Edition, incremental backups have typically been limited to Enterprise Edition.Data IndependenceAn important point about database systems is that the database should exist independently of any of the specific applications. Traditional data processing applications are data dependent. COBOL programs contain file descriptions and record descriptions that carefully describe the format and characteristics of the data.Users should be able to change the structure of the database without affecting the applications that use it. For example, suppose that the requirements of yourapplications change. A simple example would be expanding ZIP codes from five digits to nine digits. On a traditional approach using COBOL programs each individual COBOL application program that used that particular field would have to be changed, recompiled, and retested. The programs would be unable to recognize or access a file that had been changed and contained a new data description; this, in turn, might cause disruption in processing unless the change were carefully planned.Most database programs provide the ability to change the database structure by simply changing the ZIP code field and the data-entry form. In this case, data independence allows for minimal disruption of current and existing applications. Users can continue to work and can even ignore the nine-digit code if they choose. Eventually, the file will be converted to the new nine-digit ZIP code, but the ease with which the changeover takes place emphasizes the importance of data independence.Data IntegrityData integrity refers to the accuracy, correctness, or validity of the data in the database. In a database system, data integrity means safeguarding the data against invalid alteration or destruction arise. The first has to do with many users accessing the database concurrently. For example, if thousands of travel agents and airline reservation clerks are accessing the database concurrently. For example, if thousands of travel agents and airline reservation clerks are accessing the same database at once, and two agents book the same seat on the same flight, the first agent’s booking will be lost. In such case the technique of locking the record or field provides the means for preventing one user from accessing a record while another user is updating the same record.The second complication relates to hardwires, software, or human error during the course of processing and involves database transactions treated as a single . For example, an agent booking an airline reservation involves several database updates (i.e., adding the passenger’s name and address and updating the seats-available field), which comprise a single transaction. The database transaction is not considered to be completed until all updates have been completed; otherwise, none of the updates will be allowed to take place.Data SecurityData security refers to the protection of a database against unauthorized or illegal access or modification. For example, a high-level password might allow a user to read from, write to, and modify the database structure, whereas a low-level password history of the modifications to a database-can be used to identify where and when a database was tampered with and it can also be used to restore the file to its original condition.三、Choosing between Oracle and SQL ServerI have to decide between using the Oracle database and WebDB vs. Microsoft SQL Server with Visual Studio. This choice will guide our future Web projects. What are the strong points of each of these combinations and what are the negatives?Lori: Making your decision will depend on what you already have. For instance, if you want to implement a Web-based database application and you are a Windows-only shop, SQL Server and the Visual Studio package would be fine. But the Oracle solution would be better with mixed platforms.There are other things to consider, such as what extras you get and what skills are required. WebDB is a content management and development tool that can be used by content creators, database administrators, and developers without any programming experience. WebDB is a browser-based tool that helps ease content creation and provides monitoring and maintenance tools. This is a good solution for organizations already using Oracle. Oracle also scales better than SQL Server, but you will need to have a competent Oracle administrator on hand.The SQL Sever/Visual Studio approach is more difficult to use and requires an experienced object-oriented programmer or some extensive training. However, you do get a fistful of development tools with Visual Studio: Visual Basic, Visual C++, and Visual InterDev for only $1,619. Plus, you will have to add the cost of the SQL Server, which will run you $1,999 for 10 clients or $3,999 for 25 clients-a less expensive solution than Oracle’s.Oracle also has a package solution that starts at $6,767, depending on the platform selected. The suite includes not only WebDB and Oracle8i butalso other tools for development such as the Oracle application server, JDeveloper, and Workplace Templates, and the suite runs on more platforms than the Microsoft solution does. This can be a good solution if you are a start-up or a small to midsize business. Buying these tools in a package is less costly than purchasing them individually.Much depends on your skill level, hardware resources, and budget. I hope this helps in your decision-making.Brooks: I totally agree that this decision depends in large part on what infrastructure and expertise you already have. If the decision is close, you need to figure out who’s going to be doing the work and what your priorities are.These two products have different approaches, and they reflect the different personalities of the two vendors. In general, Oracle products are designed for very professional development efforts by top-notch programmers and project leaders. The learning period is fairly long, and the solution is pricey; but if you stick it out you will ultimately have greater scalability and greater reliability.If your project has tight deadlines and you don’t have the time and/or money to hire a team of very expensive, very experienced developers, you may find that the Oracle solution is an easy way to get yourself in trouble. There’s nothing worse than a poorly developed Oracle application.What Microsoft offers is a solution that’s aimed at rapid development and low-cost implementation. The tools are cheaper, the servers you’ll run it on are cheaper, and the developers you need will be cheaper. Choosing SQL Sever and Visual Studio is an excellent way to start fast.Of course, there are trade-offs. The key problem I have with Visual Studio and SQL Server is that you’ll be tied to Microsoft operating systems and Intel hardware. If the day comes when you need to support hundreds of thousands of users, you really don’t have anywhere to go other than buying hundreds of servers, which is a management nightmare.If you go with the Microsoft approach, it sounds like you may not need morethan Visual Interdev. If you already know that you’re going to be developing ActiveX components in Visual Basic or Visual C++, that’s warning sign that maybe you should look at the Oracle solution more closely.I want to emphasize that, although these platforms have their relative strengths and weaknesses, if you do it right you can build a world-class application on either one. So if you have an organizational bias toward one of the vendors, by all means go with it. If you’re starting out from scratch, you’re going to have to ask yourself whether your organization leans more toward perfectionism or pragmatism, and realize that both “isms”have their faults.中文译文：数据库管理数据库（也称DataBase）也称为电子数据库，是指由计算机特别组织的用下快速查找和检索的任意的数据或信息集合。
管理信息系统外文翻译 (2)
毕业设计（论文）外文文献翻译毕业设计（论文）题目翻译（1）题目管理信息系统翻译（2）题目数据库管理系统的介绍学院计算机学院专业姓名班级学号Management Information SystemIt is the MIS(Management Information System ) that we constantly say that the management information system , and is living to emphasize the administration , and emphasizes that it changes into more and more significantly and more and more is universalized in the contemporary community of message . MIS is a fresh branch of learning, and it leaped over several territories, and for instance administers scientific knowledge, system science, operational research, statistic along with calculating machine scientific knowledge. Is living on these the branches of learning base, and takes shape that the message is gathered and the process means, thereby take shape the system that the crossbar mingles.1. The Management Information System Summary20 centuries, in the wake of the flourishing development of whole world economy, numerous economists propose the fresh administration theory one by one. Xi Men propose the administration and was dependent on idea to message and decision of strategic importance in the 50’s 20 centuries. The dimension of simultaneous stage is admitted issuing cybernetics, and he thinks that the administration is a control procedure. In 1958, Ger. write the lid: “ the administration shall obtain without delay with the lower cost and exact message, completes the better control “. This particular period, the calculating machine starts being used accountancy work. The data handling term has risen.In 1970, Walter T.Kennevan give administration that has raised the only a short while ago information system term to get off a definition: “ either the cover of the book shape with the discount, is living appropriately time to director, staff member along with the outside world personnel staff supplies the past and now and message that internal forecasting the approaching relevant business reaches such environment, in order to assist they make a strategic de cision”. Is living in this definition to emphasize, yet does not emphasize using the pattern, and mention the calculating machine application in the way of the message support decision of strategic importance.In 1985, admonishing information system originator, title Buddhist nun Su Da university administration professor Gordon B.Davis give the management information system relatively integrated definition, in immediate future “ administer the information system is one use calculating machine software and hardware resources along with data bank man - the engine system.It be able to supply message support business either organization operation, administration or the decision making function. Comprehensive directions of this definition management information system target and meritorious service capacity and component, but also make known the management information system to be living the level that attains at that time.1.1 The Developing History of MISThe management information system is living the most primarily phase iscounting the system, the substance which researched is the regular pattern on face between the incremental data, it what may separate into the data being mutually related and more not being mutually related series, afterwards act as the data conversion to message.The second stage is the data are replaced the system, and it is that the SABRE that the American airline company put up to in the 50’s 20 centuries subscribes to book the bank note system that such type stands for. It possess 1008 bank note booking spots, and may access 600000 traveler keep the minutes and 27000 flight segments record. Its operation is comparatively more complex, and is living whatever one “spot ”wholly to check whether to be the free place up some one flight n umbers. Yet through approximately attending school up to say, it is only a data and replaces the system, for instance it can not let know you with the bank note the selling velocity now when the bank note shall be sell through, thereby takes remedying the step. As a result it also is administer information system rudimentary phase.The third phase is the status reports system, and it may separate into manufacture state speech and service state and make known and research the systems such as status reports and so on. Its type stands for the production control system that is the IBM corporation to the for instance manufacture state speech system. As is known to all, the calculating machine corporation that the IBM corporation is the largest on the world, in 1964 it given birth to middle-sized calculating machine IBM360 and causes the calculating machine level lift a step, yet form that the manufacture administration work. Yet enormously complicatedly dissolve moreover, the calculating machine overtakes 15000 difference components once more, in addition the plant of IBM extends all over the American various places to every one components once more like works an element, and the order of difference possess difference components and the difference element, and have to point out that what element what plant what installation gives birth to, hence not merely giving birth to complexly, fitting, installation and transportation wholly fully complex. Have to there be a manufacture status reports system that takes the calculating machine in order to guarantee being underway successfully of manufacture along with else segment as the base. Hence the same ages IBM establish the systematic AAS of well-developed administration it be able to carry on 450 professional work operations. In 1968, the corporation establishes the communal once more and manufactures informationsystem CMIS and runs and succeeds very much, the past needs 15 weeks work, that system merely may be completed in the way of 3 weeks.It is the data handling system that the status reports system still possess one kind of shape , and that it is used for handles the everyday professional work to make known with manufacture , and stress rests with by the handwork task automation , and lifts the effectiveness with saves the labor power . The data handling system ordinarily can not supply decision of strategic importance message.Last phase is the support systems make a strategic decision, and it is the information system being used for supplementary making a strategic decision. That system may program and the analysis scheme, and goes over key and the error solve a problem. Its proper better person-machine dialogue means, may with not particularlythe personnel staff who have an intimate knowledge of the calculating machine hold conversation. It ordinarily consists of some pattern so as to come into being decision of strategic importance message, yet emphasize comprehensive administration meritorious service capacity.1.2 The Application of Management Information SystemThe management information system is used to the most base work, like dump report form, calculation pay and occurrences in human tubes and so on, and then developing up business financial affairs administrations and inventory control and so on individual event operational control , this pertains to the electron data handling ( EDP Data Processing ) system . When establish the business data bank, thereby possess the calculating machine electric network to attain data sharing queen , the slave system concept is start off , when the implementation the situation as a whole is made program and the design information system ,attained the administration information system phase . In the wake of calculating machine technique progress and the demand adjust the system of people lift further, people emphasize more furthermore administer the information system phase. Progress and people in the wake of the calculating machine technique lift at the demand adjust the system further, people emphasize more furthermore to administer the information system whether back business higher level to lead makes a strategic decision this meritorious service capacity, still more lay special emphasis on the gathering to the external message of business and integrated data storehouse, model library , means storehouse and else artificial intelligence means whether directly to decision of strategic importance person , this is the support system ( DDS ) mission making a strategic decision.There is the part application that few business start MIS inner place the limit of the world at the early days of being living in the 70’s 20 centuries. Up at the moment, MIS is living, and there be the appropriatePopularization rate in every state nation in world, and nearly covered that every profession reaches every department.1.3 The Direction of MIS DevelopmentClose 20 curtains; external grand duke takes charge of having arisen3 kinds of alternations:A. Paying special attention to the administration being emphasized toestablishing MIS’s s ystem, and causing the administration technique headfor the ageing.B. The message is the decision of strategic importance foundation, and MISsupplies the message service in the interest of director at all times.C. Director causes such management program getting in touch with togetherwith the concrete professional work maneuver by means of MIS. not merelybig-and-middle-sized business universally establish MIS some small-sizebusiness also not exceptions of self, universally establish the communaldata network, like the electronic mail and electron data exchange and so on,MIS supplied the well support environment to the application of Intranet’stechnique to speedily developing of INTERNET especially in the past fewyears in the interest of the business.Through international technique development tendency is see, in the 90’s 20 centuries had arisen some kinds of brand-new administration technique.1. Business Processes Rebuild (BPR)A business should value correctly time and produce quality, manufacturing cost and technical service and so on several section administrations, grip at the moment organization and the process compose once more,andcompletes that meritorious service capacity integrationist, operation processization and organization form fluctuation. Shall act as the service veer of middle layer management personnel staff the decision of strategic importance of the director service?2. Intelligentization Decision Support System (IDSS)The intelligentization decision of strategic importance support system was sufficiently consider demand and the work distinguishing feature of business higher level personnel staff.3. Lean Production (LP)Application give birth to on time, comprehensive quality control and parallel project that picked amount is given birth to and so on the technique, the utmost product design cutting down and production cycle, raise produce quality and cuts down the reproduced goods to reserve, and is living in the manufacture promote corps essence, in order to meet the demand that client continuously changes.4. Agile Manufacture (AM)One kind of business administration pattern that possess the vision, such distinguishing feature is workers and staff members’ quality is high, and the organization simplifies and the multi-purpose group effectiveness GAO message loading is agile and answers client requires swiftly.2. The Effect To The Business Administration of MIS DevelopmentThe effect to the business administration of the management information system development is administered the change to business and business administration of information system development and come into being and is coming into being the far-reaching effect with.Decision of strategic importance, particularly strategic decision-making may be assisted by the administration information system, and its good or bad directly affects living and the development up the business. The MIS is impeding the orientation development that the administration means one another unites through quality and ration. This express to utilize the administration in the calculation with the different mathematical model the problem in the quantitative analysis business.The past administer that the problem is difficult to test, but MIS may unite the administration necessaries, and supply the sufficient data, and simulates to produce the term in the interest of the administration.In the wake of the development of MIS, much business sit up the decentralizedmessage concentration to establish the information system ministry of directly under director, and the chief of information system ministry is ordinarily in the interest of assistant manager’s grade. After the authority of business is centralized up high-quality administration personnel staff’s hand, as if causing much sections office work decrease, hence someone prophesy, middle layer management shall vanish. In reality, the reappearance phase employed layer management among the information system queen not merely not to decrease, on the contrary there being the increase a bit.This is for, although the middle layer management personnel staff getting off exonerate out through loaded down with trivial details daily routine, yet needs them to analyses researching work in the way of even more energy, lift further admonishing the decision of strategic importance level. In the wake of the development of MIS, the business continuously adds to the demand of high technique a talented person, but the scarce thing of capability shall be washed out gradually. This compels people by means of study and cultivating, and continuously lifts individual’s quality. In The wake of the news dispatch and electric network and file transmission system development, business staff member is on duty in many being living incomparably either the home. Having caused that corporation save the expenses enormously, the work efficiency obviously moves upward American Rank Zeros corporation the office system on the net, in the interest of the creativity of raise office personnel staff was produced the advantageous term.At the moment many countries are fermenting one kind of more well-developed manufacturing industry strategy, and become quickly manufacturing the business. It completely on the basis of the user requirement organization design together with manufacture, may carry on the large-scale cooperation in the interest of identical produce by means of the business that the flow was shifted the distinct districts, and by means of the once more programming to the machinery with to the resources and the reorganization of personnel staff , constituted a fresh affrication system, and causes that manufacturing cost together with lot nearly have nothing to do with. Quickly manufacturing the business establishes a whole completely new strategy dependence relation against consumer, and is able to arouse the structure of production once more revolution.The management information system is towards the self-adoption and Self-learning orientation development, the decision procedure of imitation man who is be able to be better. Some entrepreneurs of the west vainly hope that consummate MIS is encircles the magic drug to govern the business all kinds of diseases; Yet also someone says, and what it is too many is dependent on the defeat that MIS be able to cause on the administration. It is adaptable each other to comprehend the effect to the business of MIS, and is favor of us to be living in development and the research work, and causes the business organization and administer the better development against MIS of system and administration means , and establish more valid MIS.The Source Of Article： Russ Basiura, Mike Batongbacal管理信息系统管理信息系统就是我们常说的MIS(Management Information System), 在强调管理，强调信息的现代社会中它变得越来越重要、越来越普及。
数据库毕业设计---外文翻译
附录附录A: 外文资料翻译－原文部分：CUSTOMER TARGETTINGThe earliest determinant of success in the development of a profitable card scheme will lie in the quality of applicants that are attracted by the marketing effort. Not only must there be sufficient creditworthy applicants to avoid fruitless and expensive application processing, but it is critical that the overall mix of new accounts meets the standard necessary to ensure ultimate profitability. For example, the marketing initiatives may attract sufficient volume of applicants that are assessed as above the scorecard cut-off, but the proportion of acceptances in the upper bands may be insufficient to deliver the level of profit and lesser bad debt required to achieve the financial objectives of the scheme.This chapter considers the range of data sources available to support the development of a credit card scheme and the tools that can be applied to maximize the flow of applications from the required categories.Data availabilityThe data that makes up the ingredients from which marketing campaigns can be constructed can come from many diverse sources. Typically, it will fall into four categories:1 the national or regional register of voters;2 the national or regional register of court judgments that records the outcomeof creditor-debtor legislation;3 any national or regional pooled information showing the credit history of clients of the participating lenders; and4 commercially compiled data including and culled from name and address lists, survey results and other market analysis data, e.g. neighborhoods and lifestyle categorization through geo-demographic information systems.The availability and quality of this data will vary from country to country and bureau to bureau.Availability is not only governed by the extent to which the responsible agency has undertaken to record it, but also by the feasibility of accessing the data and the extent (if any) to which local consumer legislation or other considerations (e.g. religious principles) will allow it to be used. Other limitations on the use of available data may lie in the simple impossibility or expense of accessing the information sources, perhaps because necessary consumer consent for divulgence has been withheld or because the records are not yet stored electronically.The local credit information bureaux will be able to provide guidance on all of these matters, as will many local trade or professional associations or the relevant government departments.Data segmentation and AnalysesThe following remarks deal with the ways in which lawfully obtained data may then be processed and analyzed in order to maximize its value as the basis of a marketing prospect list. Examples of the types and uses of data that will play a role in the credit decision area are discussed later in the chapter, within the context of application processing.The key categories into which prospects may be segmented include lifestyle, propensity to purchase specific products (financial or otherwise) and levels of risk. The leading international information bureaux will be able to provide segmentation systems that are able to correlate each of these data categories to provide meaningful prospect lists in rank order. Additionally, many bureaux will have the capability to further enhance the strength and value of the data. Through the selective purchasing of data from bona fide market sources, and by overlaying generic factors deduced from the analysis of the broad mass of industry information that routinely passes through their systems, the best international operators are now able to offer marketing and credit information support that can add significantly to the quality of new applicants.The importance of the role and standard of this data in influencing the quality of the target population for mailings, etc. should not be underestimated. Information that is dated or inaccurate may not only lead a marketer and the organization into embarrassment and damage their reputations, but it will also open the credit card scheme to applicants from outside either the target sector or ,worse still, applicants outside the lender’s view of an acceptable credit risk.From this, it follows that you should seek to use an information bureau whose business principles and operating practices comply with the highest levels of both competence and integrity.Developing the prospect databaseThis is the process by which the raw data streams are brought together and subjected to progressive refinement, with the output representing the refined base from which prospecting can begin in earnest. A wide experience-often across many different markets and countries-in the sourcing, handling and analysis of data inevitably improves the quality of the ideas and systems that a bureau can offer for the development of the prospect database.In summary, the typical shape of the service available from the very best bureaux will support a process that runs as follows:1.collect and consolidate all data to be screened for inclusion;2.merge the various streams;3.sort and classify the data by market and credit categories;4.screen the date using predetermined marketing and credit criteria; and5.consolidate and output the refined list.Bureaux will charge for the use of their expertise and systems.Therefore, consideration should be given to the volumes of data that are to be processed and the costs involved at each stage. The most cost-effective approach to constructing prospect databases only undertakes the lowest-cost screening process within the earlier stages. The more expensive screening processes are not employed until the mass of the data has been reduced by earlier filtering.It is impossible to be prescriptive about the range and levels of service that are available, but reference to one of the major bureaux operating in the region could certainly be a good starting point.Campaign Management and AnalysisAgain, this is an area where excellent support is available from the best-of-breed bureaux. They will provide both the operational support and software capabilities to mount, monitor and analyse your marketing campaign, should you so wish. Their depth of experience and capabilities in the credit sector will often open up income: cost possibilities from the solicitation exercise that would not otherwise be available to the new entrant.The First Important Applications of DBMS’sData items include names and addresses of customers, accounts, loans and their balance, and the connection between customers and their accounts and loans, e.g., who has signature authority over which accounts. Queries for account balances are common, but far more common are modifications representing a single payment from or deposit to an account.As with the airline reservation system, we expect that many tellers and customers (through ATM machines) will be querying and modifying the bank’s data at once. It is vital that simultaneous accesses to an account not cause the effect of an ATM transaction to be lost. Failures cannot be tolerated. For example, once the money has been ejected from an ATM machine ,the bank must record the debit, even if the power immediately fails. On the other hand, it is not permissible for the bank to record the debit and then not deliver the money because the power fails. The proper way to handle this operation is far from obvious and can be regarded as one of the significant achievements in DBMS architecture.Database system changed significantly. Codd proposed that database system should present the user with a view of data organized as tables called relations. Behindthe scenes, there might be a complex data structure that allowed rapid response to a variety of queries. But unlike the user of earlier database systems, the user of a relational system would not be concerned with storage structure. Queries could be expressed in a very high level language, which greatly increased the efficiency of database programmers. Relations are tables. Their columns are headed by attributes.Client –Server ArchitectureMany varieties of modern software use a client-server architecture, in which requests by one process (the client ) are sent to another process (the server) for execution. Database systems are no exception, and it is common to divide the work of the components shown into a server process and one or more client processes.In the simplest client/server architecture, the entire DBMS is a server, except for the query interfaces that the user and send queries or other commands across to the server. For example, relational systems generally use the SQL language for representing requests from the client to the server. The database server then sends the answer, in the form of a table or relation, back to client. The relationship between client and server can get more complex, especially when answers are extremely large. We shall have more to say about this matter in section 1.3.3. there is also a trend to put more work in the client, since the server will be a bottleneck if there are many simultaneous database users.附录B: 外文资料翻译－译文部分：客户目标：最早判断发展可收益卡的成功性是在于受市场影响的被吸引的申请人的质量。
数据库基本原理-毕业论文外文翻译
题目（中文）基于VB的学校人事管理系统（英文）based on vb school personnel management system 学生姓名专业班完成日期：目录1. Analysis of Database Programming in VB-----------------------------231. VB的数据库编程方案分析---------------------------------------------252. Database development and application----------------------------------272.数据库的发展和应用-------------------------------------------------------------293. Basic principles of database------------------------------------------------313.数据库的基本原理-----------------------------------------------------------------33Analysis of Database Programming in VBVB (Visual Basic) is Microsoft Corporation promotes based on the Basic language visualization programming environment, but by its simple easy to study, the function formidable time the general computer amateur's favor, many application software all use VB to take the software development platform. In uses VB to develop the application software in the process, how uses the database and carries on the management for the database is all exploiter issue of concern.VB was the database programming has provided very many tools and the way, actually selected what method to carry on the database the visit to rely on user's different demand, the following on makes a simple analysis to the VB database programming way.1.DAO technologyThrough Microsoft Jet Database Engine (Jet database engine), DAO (Data Access Object) the technology mainly provides visit to ISAM (smooth index search method) type database, like realization visit to database and so on FoxPro, Access, Dbase.1.1 uses Data to controlData controls are uses in the toolbox “Data” the button to produce. Should control to have 3 basic attributes: Connect, Database Name and RecordSource.Connect attribute specified data controls the database type which must visit, the default is the Access database; The Database Name attribute value for contains the complete way the database filename; The Record Source attribute value for the record compendium which must visit, may be shows, but also SQL sentence. If visits under D plate TEMP folder teacher mdb in the database file table stud,then Data controls the Connect attribute for spatially, the Database Name attribute is “D: \ temp \ teacher mdb”, the Record Source attribute value is “stud”.Like this realized Data to control and between the database recording data binding, through transferred Data to control method realizations and so on the Add new, Update, Delete, Move last visit to the database each kind of request, when carried on the database content browsing, Data controlled also frequently to control the coordinate use with Degrade, provided the grid way the data inquiry.1.2 uses the DAO object storehouseThe DAO object storehouse model mainly uses the hierarchical structure, Dentine is the topmost story object, below has Errors and the workspace two object sets, under the workspace object is the Databases set. Quotes the DAO object storehouse when the application procedure, only can produce a Dentine object, and produces a default automatically working space object workspace, in other has not assigned in the situation, all database operation all is in workspace(0) carries out in the default work area, but must pay attention: The Jet engine starts after VB cannot load automatically, only then chooses References in the Project menu item, then selects Microsoft DAO 3.5 Object Library only then to be possible to use. uses the Create Database method foundation database in DAO, with the CreateTableDef method foundation table, opens the database with the Open Database method which assigns, opens the record compendium with the Open record set method, uses Add new, Update, Delete, Move first, Edit methods and so on record set object to be possible to realize for table each kind of operation.Through the DAO other method transfer, may realize to the table other operations.1.RDO technologyRDO is provides to relates the ODBC data pool visit connection. When needs to visit other database like SQL Server, Oracle, when specially needs to establish the customer/server application procedure, may use the long range data to control RDC (Remote Data Control) and long range data object RDO (Remote Data Control) realizes through the ODBC driver visit to the database.Uses ODBC visits when some database must first install the corresponding driver, establishes a data pool, through data pool visit corresponding database which assigns. Establishes the ODBC data pool is turns on “the control panel” the window, double-clicks the ODBC executive program the icon, in opens in the ODBC data pool supervisor dialog box single-clicks “Add” the button to found the data pool, and chooses corresponding database.2.1 uses RDC to controlControls with DATA to be very similar in the use, assigns with the Data source name attribute to control a binding the data source name, assigns the record compendium with the SQL attribute, different is, controls in the SQL attribute in RDC to have to use the SQL sentence to assign. When database browsing also frequently controls the union use with DBGrid.2.2 uses the RDO object storehouseIn uses in front of the RDO object, should choose References in the Project menu item, after selects “Microsoft Remote Data Object 2.0”only then to be possible to use.uses RDO to visit the ODBC data pool the step is:(1) Establishes a RDO environment object.(2) Uses the Open connection method to open an ODBC data pool.(3) Uses the Open Result set method to establish the result collection object.(4) Use assigns the method, carries on each kind of operation to the result centralism recording.After founds the as this result collection object, is similar with the DAO object storehouse use, may through transfer method realizations and so on its Add new, Update, Delete visit to assign the data pool each kind of request.3.ADO technologyADO (ActiveX Data Objects) is the Microsoft most recent data accessing technology, he uses general data accessing connection UDA (Universal Data Access), all data standard will be one kind of data pool, passes through OLE the DB connection filtration, transforms one kind of general data format by the same way, enables the application procedure to visit this kind of data.OLE DB is an underlying bed data accessing connection, may visit each kind of data pool with him, including traditional relations database, as well as electronic mail system and from definition commercial object.3.1 uses ADO to controlsingle-clicks the Components order in the Project menu, selects “Microsoft ADO Data Control in the Components dialog box 6.0 (OLE DB)”, may control ADO to increase to controls in a box.controls the Connection string attribute through ADO to establish the database file which OLE DB Provider and assigns, the Record Source attribute establishes ADO to control the connected record source. Are similar with DAO and RDO, controls through ADO with the recording source connection, may realize to each kind of database fast access.3.2 uses the ADO object storehouseSingle-clicks the References order in the Project menu, selects “Microsoft ActiveX Data Objects 2.0 Library” in the References dialog box, may increase in the project to the ADO object storehouse quotation.Beforehand object model, like DAO and RDO all are the level, low data object like Record set is several high level object like Environment and the Queried sub-object. But ADO is actually different, he has defined a group of plane top object, the most important 3 ADO object is Connection, Record set and Command.The Connection object uses in establishing the application procedure and the data pool connection; The Command object uses in defining a SQL sentence, a memory process or other carries on the operation to the data the order; After the Record set object preservation execution order returns record compendium.Through transfers the Record set object the alternative means, may realize to operations and so on record compendium revision, deletion, inquiry.4 conclusionsVB provided the very many method realization to the database operation, in which DAO main realization visit to ISAM database, RDO has provided to the ODBC data pool connection, RDO and DAO all has developed for the quite mature technology, in VB in front of 6.0 is the main database visit technology, but Active Data Objects(ADO) the recent generation of database interface which promotes as Microsoft, is designed with recent data accessing level OLE DB the Provider together joint operation, provides the general data accessing (Universal Data Access), he has provided very many advantage to the VB programmer, including easy to use, the familiar contact surface, the high velocity as well as the low memory takes (Has realized ADO2.0 Msado15.dll to need to take the 342K memory, is slightly smaller than RDO Msrdo20.dll 368K, probably is DAO3.5 Dao350.dll occupies the memory 60%), as a result of above reason, ADO gradually will replace other data accessing connection, will become the VB visit database the fundamental mode.VB的数据库编程方案分析VB（Visual Basic）是微软公司推出的基于Basic语言的可视化编程环境,以其简单易学、功能强大而倍受广大电脑爱好者的青睐，许多应用软件都采用VB作为软件开发平台。
(完整word版)数据库管理系统介绍 外文翻译
外文资料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 subsystem that 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 as its 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 recordwould 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 information without 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 dataformats. 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 thelocation 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也可以称为电子数据库，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。
数据库外文文献翻译
Transact-SQL Cookbook第一章数据透视表1.1使用数据透视表1.1.1 问题支持一个元素序列往往需要解决各种问题。
例如，给定一个日期范围，你可能希望产生一行在每个日期的范围。
或者，您可能希望将一系列的返回值在单独的行成一系列单独的列值相同的行。
实现这种功能，你可以使用一个永久表中存储一系列的顺序号码。
这种表是称为一个数据透视表。
许多食谱书中使用数据透视表，然后，在所有情况下，表的名称是。
这个食谱告诉你如何创建表。
1.1.2 解决方案首先，创建数据透视表。
下一步，创建一个表名为富，将帮助你在透视表：CREATE TABLE Pivot (i INT,PRIMARY KEY(i))CREATE TABLE Foo(i CHAR(1))富表是一个简单的支持表，你应插入以下10行：INSERT INTO Foo VALUES('0')INSERT INTO Foo VALUES('1')INSERT INTO Foo VALUES('2')INSERT INTO Foo VALUES('3')INSERT INTO Foo VALUES('4')INSERT INTO Foo VALUES('5')INSERT INTO Foo VALUES('6')INSERT INTO Foo VALUES('7')INSERT INTO Foo VALUES('8')INSERT INTO Foo VALUES('9')利用10行在富表，你可以很容易地填充枢轴表1000行。
得到1000行10行，加入富本身三倍，创建一个笛卡尔积：INSERT INTO PivotSELECT f1.i+f2.i+f3.iFROM Foo f1, Foo F2, Foo f3如果你名单上的行数据透视表，你会看到它所需的数目的元素，他们将编号从0到999。
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吉林化工学院理学院毕业论文外文翻译阿德里恩.甘卡，伊莫.盖格尔罗马尼亚布加勒斯特迪杜奥列斯库大学德国派尔博登施泰特威廉学校数据库优化服务Database Optimizing Services学生学号：********学生姓名：***专业班级：信息与计算科学0801 指导教师：***职称：教授起止日期：2012.2.27～2012.3.14吉林化工学院Jilin Institute of Chemical Technology数据库优化服务摘要几乎每一个组织都存在它的中心数据库。
数据库为不同的活动提供支持，无论是生产，销售和市场营销或内部运作。
为了获得战略决策的帮助，一个数据库每天都在被访问。
要满足这种需求，因此需要与高品质的安全性和可用性。
为实现一些需求所使用的DBMS（数据库管理系统），事实上，是一个数据库软件。
从技术上讲，它是软件，它采用了标准的编目，恢复和运行不同的数据查询方法。
DBMS 管理输入数据，组织安排这些数据，并提供它的用户或其他程序修改或提取数据的方法。
数据库管理就是一种需要定期更新，优化和监测的操作。
关键词数据库，数据库管理系统（DBMS），索引，优化，成本，优化数据库。
1 引言该文件的目的是介绍有关数据库的基本优化代表的观念，在不同类型的查询中使用数学估计成本，可以达到性能水平的审查，以及分析在特定查询的例子中不同的物理访问结构的影响。
目标群体应该熟悉SQL在关系数据库的基本概念。
通过这种方式，可以执行复杂的查询策略，允许以较低的成本获得信息的使用知识。
一个数据库经过一系列转换，直到其最终用途，以数据建模，数据库设计和开发为开始，以维护和优化为结束。
2 数据库建模2.1 数据建模数据模型更侧重于数据是必要的，而做出数据的方式应该是一种有组织的和少操作的方式。
数据建模阶段涉及结构的完整性，操作和查询。
这有多个这方面的事项，如：1。
数据定义方式应该是有组织的（分层网络，关系和重点对象）。
这需要提供一个规则，来约束实例的定义结构的允许/限制。
2。
提供了数据更新协议。
3。
提供了数据查询的方法。
一个结构简单的数据通信，能够使得最终用户很容易的理解，是数据建模想要的的实际结果。
2.2 自定义数据库/数据库发展数据库的开发和自定义答复了顾客的需求。
自定义数据库的重要性主要体现在通过它，使向目标客户直接提供服务的产品的商业化成为可能。
一个数据库的质量通过定期更新来维护。
2.3 数据库设计如果数据库有以下任何问题，如故障，不安全或不准确的数据或数据库退化，失去了其灵活性，那么是时候换新数据库了。
因此，必须定义具体的数据类型和存储机制以便通过规则和正确地运用操作机制，确保数据的完整性。
所有数据库应构建一个客户方面的规范，包括它的用户界面和功能。
通过这些可以使运用数据进入一个网站成为可能。
2.4 数据挖掘数据挖掘是科学从更大的数据集和数据库中提取有用信息。
每个组织都希望其业务和进行流程可以进行优化实现最佳生产力。
优化业务流程所需要的，包括客户关系管理（CRM），质量控制，价格和交货系统等。
数据挖掘是指一个数据开发自我违规，即通过使用复杂的算法彰显在这些过程中的错误的过程。
数据挖掘的进行主要是处理数据，包括失误分析和测试。
2.5 数据库迁移数据库迁移，基本数据库的转让（或迁移）方案和数据进入数据库管理的过程，如甲骨文，IBM的DB2，MS-SQL的服务器，My-SQL等。
一个数据库迁移系统，需保持数据可靠性和完整性。
因为标准之间的差异，从一个数据库平台迁移应该是困难且费时的，然而，不同的数据库之间的数据，在确保数据的完整性的前提下，快速迁移是可能的，可以没有任何数据丢失。
对数据访问的保障及其保护是必不可少的，尤其是当大量的数据或重要的应用在系统之间移动时。
在投影和运用Oracle或Microsoft SQL Server 数据库基础设施中提供的经验使数据的安全性、可用性和可靠性得到了保证。
2.6 数据库维护对于每一个组织，数据库维护是非常重要的过程。
在数据库安全开发后，具有重大意义的下一道工序是数据库维护，它提供了数据库的更新，备份和高安全性。
我们可以问自己，为什么公司需要数据库维护？当数据库被改变，很容易发现被观察到的记录不再反映现实。
这个问题通常在数据库恶化的情况下发生。
建议，消除任何手动更新有关的疑虑，并定期进行完整备份。
由于该结构活性的增长，数据库的维度也随着增长。
一个有用的做法是定期删除不可用数据，从而增加数据库的访问速度。
数据库压缩可以使数据供应更加容易，以及使处理数据库中相关信息更加简单化。
可以保持相同的数据库，在这种方式下，它可以针对不同的问题提供正确的结果。
例如，可以利用相同的讨论列表提取通讯地址以及电子邮件地址。
3 数据库优化数据库是在现代世界中无处不在。
“信息库”这个概念，代表持久、冗余和均匀分布，已成为IT领域中最重要的概念。
事实上，许多人通常无需使用计算机，就可以在每一天的每一时刻，在一定的水平上与数据库管理系统进行交互。
由于每次访问需要接受以百万计的数据传输，数据库优化在大学以及企业团体的研究机构的研究领域中，是一个关键。
从一个软件开发公司的角度出发，关系数据库往往成为在该领域的应用软件，以及维持客户和公司所需的重大成本所缺乏的优化部分。
随着数百万每秒的数据传输，优化作为一个惊喜，在研究领域中由此迈出了关键性的一步。
优化数据库，可以更好的配置和更快的搜索到结果。
偶尔的数据库可能会出现的问题，如未能提供所要求的结果，或缓慢的执行，这时很必要收购服务器。
在该数据库不能优化的情况下，操作系统可能有类似的作用。
通过修改当前数据库的基础设施，从而确立最佳的优化方法和规划，可以更好的提高工作环境的效率。
通过实施数据库质量监控，它可以不重复且保持高完整性的进行优化。
如今，这种优化是一个真正的挑战，特别是当前软件在不断更新变化。
但是，数据库管理员能够提供有关的解决方案以满足客户的要求。
图3-1：数据结构3.1 数据库管理应用程序数据库管理有不同的做法，也有不同的方式，优化数据库使性能得到提升，这也将提高服务器的使用。
数据库优化依赖于数据库管理系统。
每个系统都有自己进行优化的设施。
优化过程中，有一些程序有对所需的数据进行收集和分析的作用。
这些应用程序将以一种高敏锐的方式被用于数据库的优化，这样的使用也越来越显著。
随着数据库系统变得越来越重要，一个数据库的持续更新是必很必要的，这样才能保持与IT领域的变化同步。
3.2 索引一个数据库的各种优化途径之一是索引。
它可以增加从一个数据库到另一个不同的数据库间的查询性能。
但是，一般来说，用户更受益于高效的索引。
高效的索引可以避免扫描整个结构表来进行查询来确定解决方案。
这种索引可以通过Microsoft SQL服务器来实现，SQL服务器已经取得了相关的指标集。
此外，为了让在查询处理中进行最有效的选择，它的保持永久性更新。
在提高查询的性能这方面，专家提供的意见是，由于数据库的性能必须要更新，所以必须考虑在动力系统的变化。
数据库管理系统提供了其自己的更新方式，如Oracle，它包括一个SQL型“顾问”和另外一个访问“顾问”。
这些都是用来改善在打包应用程序中被使用的SQL。
它使用样本来收集必要的数据更新。
优化是保持系统最佳性能的最重要途径之一。
他们可以有不同的名字，但本质上它们有助于提高系统的性能。
数据库优化包含在该持有人可以使用的软件中。
他们指的是只有IT专家可以使用的一种更复杂的方式。
如今，这种应用程序提供提高优化效率的特性，为了能够保持数据库的生命周期，持有人需确保他们数据库的先进性。
3.3使用索引优化数据库数据库索引是一个数据库表的物理访问结构，顾名思义，它是一个有序的文件，通报位于光盘上登记的数据库的去向。
为了更好地理解索引做的是什么，请考虑阅读一本教科书。
为了找到某个部分，读者可以读这本书，直到他所发现他寻找的，或者可以检查的“目录”，找到所需的部分。
数据库索引可以比教科书索引长得多。
在一个大表中添加足够的索引在优化数据库中是最重要的组成部分。
为不包含任何索引的一个大表创造唯一索引，可以大大降低查询的执行时间。
举个例子，假设有下列情景：有一个数据库表名为“雇员” ，有100份登记数据，我们想在这个未索引的表上执行下面的一个简单查询：从第一个名字到最后一个名字中查找ID为12345的人。
为找出上述ID与登记的雇员，数据库需扫描整个登记的100数据以返回正确的结果。
这种扫描方式，通常被称为全表的扫描。
幸运的是，数据库开发人员可以创建一列雇员ID的索引以防止这种扫描。
此外，在该数据库的域名受到唯一性约束的情况下，可以编译表中的每个雇员的物理地址，且地址是实时登记的，因此，扫描变得毫无意义。
增加了这个索引列的开发后，数据库可以找到雇员ID与12345相同的雇员登记，这潜在的减少了100份数据的查询操作。
3.4索引类型索引包括两种类型：聚集和非聚集。
两个类别之间的主要区别是，聚集不影响索引在硬盘上的排序，而非聚集索引不行，由于聚集索引不影响在光盘上的物理登记顺序，所以可以为每个表建索引群集。
同样的限制不能适用于非聚集索引，从而在光盘上创造的空间是可能的（虽然它不代表最佳的解决方案）。
3.5 优化数据库的成本估算成本估算是对某一查询费用采用一致的、重要的措施的执行过程。
不同的度量，可实现这一目标，但最相关和最常见的度量是块访问查询车。
由于磁盘上的输入/输出是很耗时的操作。
因此，成本估算的目标是在不影响正常功能的前提下最大限度地减少块访问数量。
数据库有一系列的成本优化方法，查询操作的估计成本，注册操作估计成本，嵌套循环，单回路（使用索引）和排序合并注册等都可以考虑在内。
每个方法的最终其结果都减少了算法的复杂性。
这些所使用的技术之一，是GREEDY的技术。
GREEDY算法在用于优化问题时大体上是很简单的。
例如，找到一个最简单的路径图表，在大多数情况下，我们有如下方案元素：●大量元素（图形的顶点，工程进度等）;●一个函数，用来检测候选人的规模是可能的，虽然不一定是最优的解决方案；●一个函数，用来检测候选人的竞争对手的规模是可能的，虽然不一定是最优的解决方案；●一个查询功能，查询在任何特定时间未使用的最佳元素；●一个函数，通知用户已达成的一个解决方案。
为了解决这个问题，GREEDY算法可以一步一步的建立解决方案。
GREEDY的技术状态即结构因素的数量（图中的节点和弧）指的是安排大量候选人的工作量的指数。
在同一时间内，当有很大数量的候选人安排的情况下，靠主体算法来解决这个工作量不是可行。
减少GREEDY技术根系的结构因素数量就是GREEDY算法：如果工作量是一个序列，那么该算法被命名为GREEDY-SQL；GREEDY-SQL的算法使用UnionPar功能。