Les04-数据库设计范式

数据库设计与范式理论数据库设计是指在数据库系统中按照一定的规范和要求，对数据进行组织、设计和管理的过程。

范式理论是建立在关系模型基础上，用于规范化数据库中数据的一套理论原则。

本文将介绍数据库设计以及范式理论的基本概念和应用。

一、数据库设计的概述数据库设计是数据库开发过程中的重要一环，它直接影响着数据库的性能、数据的完整性和安全性等方面。

一个合理的数据库设计可以提高系统的性能和可靠性。

1. 数据库设计的步骤数据库设计通常包括以下几个步骤：- 需求分析：明确数据库的需求，包括数据类型、数据量、数据关系等。

- 概念设计：根据需求分析结果，设计数据库的概念结构，主要包括实体、属性和关系等。

- 逻辑设计：将概念设计转化为逻辑模型，通常使用ER图或UML 类图表示。

- 物理设计：将逻辑模型转化为物理模型，确定数据存储结构和索引等细节。

- 实施与维护：根据物理设计结果，创建数据库，进行数据导入、备份和恢复等操作。

2. 数据库设计的原则数据库设计应遵循以下原则：- 数据库的一致性：确保数据库中的数据不重复、不冗余。

- 数据库的完整性：保证数据的完整性，防止数据丢失或损坏。

- 数据库的性能：优化数据库查询和更新操作，提高系统性能。

- 数据库的安全性：采取措施保护数据库免受未授权访问和数据泄露的风险。

二、范式理论的基本概念范式理论是数据结构中的一个重要理论框架，主要用于规范化数据库中的数据。

下面介绍数据库设计中常用的三个范式：第一范式(1NF)、第二范式(2NF)和第三范式(3NF)。

1. 第一范式(1NF)第一范式要求数据库表中的每个字段具有原子性，即每个字段不可再分。

同时，每个字段在表中的位置也是固定的。

2. 第二范式(2NF)第二范式要求数据库表中的每个非主键字段完全依赖于主键，即非主键字段不能部分依赖于主键。

如果存在部分依赖，需要将其拆分为多个表。

3. 第三范式(3NF)第三范式要求数据库表中的每个非主键字段不依赖于其他非主键字段，即非主键字段之间不存在传递依赖关系。

Copyright © 2008, Oracle. All rights reserved. Managing the Oracle Instancex i n h uz h an g(z ah u gg@g ma i l.c o m)h as an o n-t r an s fe r ab l el i c en s et ou s et h i sS t ud e nt Gu i de.Copyright © 2008, Oracle. All rights reserved.ObjectivesAfter completing this lesson, you should be able to dothe following:•Start and stop the Oracle database andcomponents•Use Enterprise Manager (EM)•Access a database with SQL*Plus and i SQL*Plus •Modify database initialization parameters •Describe the stages of database startup •Describe the database shutdown options •View the alert log •Access dynamic performance views x i n h u z h a n g (za h u g g @g m a i l .c o m) h a s a n o n -t r a n s f e r a b l e l i c e n s e t o u s e t h i s S t u d e n t G u i d e .Copyright © 2008, Oracle. All rights reserved.Management FrameworkThe three components of the OracleDatabase 10g management framework are:•Database instance•Listener•Management interface –Database Control–Management agent (when using Grid Control)Listener Database Control ManagementagentManagement interface -or->Components SQL*Plus Init Params DB Startup DB Shutdown Alert Log Perf ViewsManagement Framework There are three major components of the Oracle database management framework:•The database instance that is being managed• A listener that allows connections to the database•The management interface. This may be either a management agent running on thedatabase server (which connects it to Oracle Enterprise Manager Grid Control)or thestand-alone Oracle Enterprise Manager Database Control. This is also referred to asDatabase Console.Each of these components must be explicitly started before you can use the services of thecomponent and must be shut down cleanly when shutting down the server hosting theOracle database.The first component to be started is the management interface. After this is activated, themanagement interface can be used to start the other components.x i n h u z h a n g (z a h u g g @g m a i l .c o m ) h a s a n o n -t r a n s f e r a b l e l i c en s e t o u s e t h i s S t u d e n t G u i d e .Copyright © 2008, Oracle. All rights reserved.Starting and Stopping Database Control$ emctl start dbconsoleTZ set to US/PacificOracle Enterprise Manager 10g Database Control Release 10.2.0.1.0Copyright (c) 1996, 2005 Oracle Corporation. All rights reserved.:1158/em/console/aboutApplicationStarting Oracle Enterprise Manager 10g Database Control............. started.------------------------------------------------------------------Logs are generated in directory/u01/app/oracle/product/10.2.0/db_1/_orcl/sysman/log$ emctl stop dbconsoleTZ set to US/PacificOracle Enterprise Manager 10g Database Control Release 10.2.0.1.0Copyright (c) 1996, 2005 Oracle Corporation. All rights reserved.:1158/em/console/aboutApplicationStopping Oracle Enterprise Manager 10g Database Control ...... Stopped.Starting and Stopping Database Control Oracle provides a stand-alone management console called Database Control for databases that are not connected to the Grid Control framework. Each database that is managed withDatabase Control has a separate Database Control installation, and from any one DatabaseControl, you can manage only one database. Before using Database Control, ensure that adbconsole process is started.To start the dbconsole process, use the following command:emctl start dbconsole To stop the dbconsole process, use the following command:emctl stop dbconsoleTo view the status of the dbconsole process, use the following command:emctl status dbconsoleNote:You may need to navigate to your $ORACLE_HOME/bin directory if this directoryis not in your operating system (OS) path.Database Control uses a server-side agent process. This agent process automatically startsand stops when the dbconsole process is started or stopped.x i n h u z h a n g (z a h u g g @g m a i l .c o m ) h a s a n o n -t r a n s f e r a b l e l i c en s e t o u s e t h i s S t u d e n t G u i d e .Copyright © 2008, Oracle. All rights reserved.Oracle Enterprise ManagerOracle Enterprise Manager When you install an Oracle database, Oracle Universal Installer also installs Oracle Enterprise Manager (Enterprise Manager). Its Web-based Database Control serves as theprimary tool for managing your Oracle database. You can access online help from any ofthe pages to assist you with the task at hand. You can drill down into links in mostsituations, where there is more specific information to be had about the contents of a page. Although you may sometimes want to write and execute commands that you composeyourself, Enterprise Manager provides a graphical interface for doing almost any task thatyou would have to do as a database administrator (DBA). Viewing alert summaries andperformance graphs, creating and modifying objects, and performing backup and recovery are some of the things that you can do with Enterprise Manager.x i n h u z h a n g (z a h u g g @g m a i l .c o m ) h a s a n o n -t r a n s f e r a b l e l i c en s e t o u s e t h i s S t u d e n t G u i d e .Copyright © 2008, Oracle. All rights reserved.Accessing Oracle Enterprise ManagerAccessing Oracle Enterprise Manager Open your Web browser, and enter the following URL:http://host name :port number /em If the database is:•Up:Enterprise Manager displays the Database Control Login page. Log in to thedatabase by using a username that is authorized to access Database Control. Initially,this is SYS , SYSMAN , or SYSTEM . Use the password that you specified for theaccount during the database installation. In the Connect As option, select eitherSYSDBA or SYSOPER to log in to the database with special database administrationprivileges.•Down:Enterprise Manager displays the Startup/Shutdown and Perform Recoverypage. If this is the case, click the Startup/Shutdown button. You are then promptedfor the host and target database login usernames and passwords, which you mustenter.Note:If you have trouble starting Enterprise Manager, ensure that a listener is started.x i nh u z h a n g (z a h u g g @g m a i l .c o m ) h a s a n o n -t r a n s f e r a b l e l i c en s e t o u s e t h i s S t u d e n t G u i d e .Copyright © 2008, Oracle. All rights reserved.Database Home PageProperty pagesDatabase Home Page The Database Home page displays the current state of the database by displaying a series of metrics that portray the overall health of the database. With the property pages, whichare also referred to as tabs, you can access the Performance, Administration, andMaintenance pages for managing your database.You can view the following performance and status information about your databaseinstance on the Database Home page:•Instance name, database version, Oracle home location, media-recovery options, andother pertinent instance data•Current instance availability•Outstanding alerts•Session-related and SQL-related performance information•Key space usage metrics•Drill-down links (for example, LISTENER_<host_name >) to provide increasinglevels of detail x i n h u z h a n g (z a h u g g @g m a i l .c o m ) h a s a n o n -t r a n s f e r a b l e l i c en s e t o u s e t h i s S t u d e n t G u i d e .Copyright © 2008, Oracle. All rights ing SQL*Plus and i SQL*Plusto Access Your DatabaseSQL*Plus and i SQL*Plus provide additionalinterfaces to your database to:•Perform database management operations•Execute SQL commands to query, insert, update,and delete data in your database Components >SQL*Plus Init Params DB Startup DB Shutdown Alert Log Perf ViewsUsing SQL*Plus and i SQL*Plus to Access Your Database In addition to Enterprise Manager, you can use other Oracle tools, such as SQL*Plus and i SQL*Plus, to issue SQL statements. These tools enable you to perform many of thedatabase management operations as well as to select, insert, update, or delete data in the database.x i n h u z h a n g (z a h u g g @g m a i l .c o m ) h a s a n o n -t r a n s f e r a b l e l i c en s e t o u s e t h i s S t u d e n t G u i d e .Copyright © 2008, Oracle. All rights ing i SQL*Plus123Using i SQL*Plus i SQL*Plus is a browser-based interface to an Oracle database. It is a component of the SQL*Plus product. i SQL*Plus has a server-side listener process that must be started beforeyou can connect with a browser. To start this server process, use:isqlplusctl start After the server process is started, connect to it by entering the following URL in abrowser:http://host name :port /isqlplusThe port number that is used by i SQL*Plus is usually 5560 unless Oracle UniversalInstaller (OUI) detects that something is already using that port. Check$ORACLE_HOME/install/portlist.ini to find the port used by i SQL*Plus.x i n h u z h a n g (z a h u g g @g m a i l .c o m ) h a s a n o n -t r a n s f e r a b l e l i c en s e t o u s e t h i s S t u d e n t G u i d e .Copyright © 2008, Oracle. All rights reserved.Setting Up i SQL*Plusfor SYSDBA and SYSOPER AccessFor a user to login to i SQL*Plus as SYSDBA or SYSOPERyou must set up the user in the OC4J user manager byperforming the following steps:1.Create a user2.Grant the webDba role to the user$ cd $ORACLE_HOME/oc4j/j2ee/isqlplus/\> application-deployments/isqlplus$JAVA_HOME/bin/java \> -Djava.security.properties=\> $ORACLE_HOME/oc4j/j2ee/home/config/jazn.security.props \> -jar $ORACLE_HOME/oc4j/j2ee/home/jazn.jar \> -user "iSQL*Plus DBA/admin" -password welcome -shellJAZN> adduser "iSQL*Plus DBA" username passwordJAZN> grantrole webDba "iSQL*Plus DBA" usernameSetting Up i SQL*Plus for SYSDBA and SYSOPER Access When the i SQL*Plus Connection Role page appears, notice that the SYSOPER and SYSDBA roles require special setup and authentication for security reasons. To do this,you must set up a user in the Oracle Application Server Containers for J2EE (OC4J) user manager and grant access to the webDba role for the user. Do this by performing the following steps. Note that the JAVA_HOME OS environment variable must be set to$ORACLE_HOME/jdk .1.Change to the correct directory:cd $ORACLE_HOME/oc4j/j2ee/isqlplus/\application-deployments/isqlplus 2.Run the JAZN shell:$JAVA_HOME/bin/java \-Djava.security.properties=\$ORACLE_HOME\/oc4j/j2ee/home/config/jazn.security.props \-jar $ORACLE_HOME/oc4j/j2ee/home/jazn.jar \-user "iSQL*Plus DBA/admin" \-password welcome -shellx i n h u z h a n g (z a h u g g @g m a i l .c o m ) h a s a n o n -t r a n s f e r a b l e l i c en s e t o u s e t h i s S t u d e n t G u i d e .Setting Up iSQL*Plus for SYSDBA and SYSOPER Access (continued) 3. Create a user, choosing a username and password:JAZN> adduser "iSQL*Plus DBA" username password4. Grant the webDba role to the user:JAZN> grantrole webDba "iSQL*Plus DBA" username5. Exit the JAZN shell:JAZN> exith xinun zhagtr ona n e. has uid ) om ent G c ail. Stud m @g this ugg use h (zae nsf arl ble aicnse etoUnauthorized reproduction or distribution prohibited. Copyright© 2008, Oracle and/or its affiliates.Oracle Database 10g: Administration Workshop I 4 - 11Using SQL*PlusSQL*Plus is: • A command-line tool • Used interactively or in batch mode$ sqlplus hr/hr SQL*Plus: Release 10.2.0.1.0 - Production on Mon Jul 25 12:37:21 2005 Copyright (c) 1982, 2005, Oracle. All rights reserved. Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production With the Partitioning, OLAP and Data Mining options SQL> select last_name from employees;xtr onLAST_NAME a n e. ------------------------Abel has uid ) Ande om ent G c Atkinson ail. Stud m i @gCopyrights 2008, Oracle. All rights reserved. gg se th © u u zah ( Usingang SQL*Plus zh uYou can use the command-line interface to SQL*Plus to write SQL*Plus, SQL, and inh PL/SQL commands to:• Enter, edit, run, store, retrieve, and save SQL commands and PL/SQL blocks • Format, calculate, store, and print query results • List column definitions for any table • Send messages to and accept responses from an end user • Perform database administration To start SQL*Plus, perform the following steps: 1. Open a terminal window. 2. At the command-line prompt, enter the SQL*Plus command in the form:$ sqlplus /nologe nsf arl ble aicnse eto3. Enter connect followed by the user you want to connect as. 4. When prompted, enter the user’s password. SQL*Plus starts and connects to the default database.Unauthorized reproduction or distribution prohibited. Copyright© 2008, Oracle and/or its affiliates.Oracle Database 10g: Administration Workshop I 4 - 12Calling SQL*Plus from a Shell Script$ ./batch_sqlplus.sh SQL*Plus: Release 10.2.0.1.0 - Production on Mon Jul 25 12:47:44 2005 Copyright (c) 1982, 2005, Oracle. All rights reserved. Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production With the Partitioning, OLAP and Data Mining options # Name of this file: batch_sqlplus.sh SQL> # Count employees and give raise. COUNT(*) sqlplus hr/hr <<EOF ---------select count(*) from employees; 107 update employees set salary = SQL> salary*1.10; 107 rows updated. commit; SQL> quit Commit complete. EOF SQL> Disconnected from Oracle Database 10g Enterprise Edition Release exit 10.2.0.1.0 - Production With the Partitioning, OLAP and Data Mining options [oracle@EDRSR9P1 oracle]$OutputCalling ng SQL*Plus from a Shell Script ha call SQL*Plus from a shell script or BAT file by invoking sqlplus and using z You can huthe operating system scripting syntax for passing parameters. xin In this example, the SELECT, UPATE and COMMIT statements are executed, before SQL*Plus returns control to the operating system.tr ona n e. has uid ) om ent G c ail. Stud m i @gCopyrights 2008, Oracle. All rights reserved. gg se th © u u zah (e nsf arl ble aicnse etoUnauthorized reproduction or distribution prohibited. Copyright© 2008, Oracle and/or its affiliates.Oracle Database 10g: Administration Workshop I 4 - 13Calling a SQL Script from SQL*Plusscript.sqlselect * from departments where location_id = 1400; quitOutput$ sqlplus hr/hr @script.sql SQL*Plus: Release 10.2.0.1.0 - Production on Mon Jul 25 12:57:02 2005 Copyright (c) 1982, 2005, Oracle. All rights reserved. Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production With the Partitioning, OLAP and Data Mining options DEPARTMENT_ID DEPARTMENT_NAME MANAGER_ID LOCATION_ID ------------- ------------------------------ ---------- ----------60 IT 103 1400xtr ona n e. Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production has uid ) Mining With the Partitioning, OLAP and m o Data ent G options c $ ail. Stud m i @gCopyrights 2008, Oracle. All rights reserved. gg se th © u u zah ( Calling ng a SQL Script from SQL*Plus zha You can call an existing SQL script file from within SQL*Plus. This can be done at the u inh command line when first invoking SQL*Plus, as shown in the slide. It can also be donefrom inside a SQL*Plus session, simply by using the “@” operator. For example, this runs the script from within an already established SQL*Plus session:SQL> @script.sqle nsf arl ble aicnse etoUnauthorized reproduction or distribution prohibited. Copyright© 2008, Oracle and/or its affiliates.Oracle Database 10g: Administration Workshop I 4 - 14Initialization Parameter FilesComponents SQL*Plus > Init Params DB Startup DB Shutdown Alert Log Perf ViewsInitialization Parameter Files ng hayou start the instance, an initialization parameter file is read. There are two types of z huWhen files: xin parameter • Server parameter file: This is the preferred type of initialization parameter file. It is a binary file that can be written to and read by the database server and must not be edited manually. It resides in the server that the Oracle database is executing on, and is persistent across shutdown and startup. This is often referred to as a server parameter file (SPFILE). The default name of this file, which is automatically sought at startup, is spfile<SID>.ora. • Text initialization parameter file: This type of initialization parameter file can be read by the database server, but it is not written to by the server. The initialization parameter settings must be set and changed manually by using a text editor so that they are persistent across shutdown and startup. The default name of this file, which is automatically sought at startup if an SPFILE is not found, is init<SID>.ora. It is recommended that you create an SPFILE as a dynamic means of maintaining initialization parameters. By using an SPFILE, you can store and manage your initialization parameters persistently in a server-side disk file.Unauthorized reproduction or distribution prohibited. Copyright© 2008, Oracle and/or its affiliates.Oracle Database 10g: Administration Workshop I 4 - 15tr ona n e. has uid ) om ent G c ail. Stud m i @gCopyrights 2008, Oracle. All rights reserved. gg se th © u u zah (spfileorcl.orae nsf arl ble aicnse etoSimplified Initialization ParametersBasicAdvancedCONTROL_FILES DB_BLOCK_SIZE PROCESSES UNDO_MANAGEMENT …g Simplified Initialization Parameters han parameters are divided into two groups: basic and advanced. z huInitialization xin In the majority of cases, it is necessary to set and tune only the 32 basic parameters to get reasonable performance from the database. In rare situations, modification of the advanced parameters may be needed to achieve optimal performance. A basic parameter is defined as one that you are likely to set to keep your database running with good performance. All other parameters are considered to be advanced. The examples of basic parameters include “destinations” or directory names for specific types of files: AUDIT_FILE_DEST, BACKGROUND_DUMP_DEST, CORE_DUMP_DEST, DB_CREATE_FILE_DEST, DB_CREATE_ONLINE_LOG_DEST_n, DB_RECOVERY_FILE_DEST, and USER_DUMP_DEST.Initialization Parameters: Examples The CONTROL_FILES parameter specifies one or more control file names. Oracle strongly recommends that you multiplex and mirror control files. The range of values for this parameter is from 1 to 8 file names (with path names). The default range is OS dependent.Unauthorized reproduction or distribution prohibited. Copyright© 2008, Oracle and/or its affiliates.Oracle Database 10g: Administration Workshop I 4 - 16) ha t Guid m .co den il ma s Stu g i g@ Copyright © 2008, Oracle. All rights reserved. g se th u u zah (l DB_CACHE_SIZE ble DB_FILE_MULTIBLOCK fera s _READ_COUNT tran SHARED_POOL_SIZE non s…a e.icnse etoSimplified Initialization Parameters (continued) Initialization Parameters: Examples (continued) The DB_BLOCK_SIZE parameter specifies the size (in bytes) of an Oracle database block. This value is set at database creation and cannot be subsequently changed. Range of values: 2048–32768 (OS dependent). Default value: 8K (OS dependent). The DB_CACHE_SIZE parameter specifies the size of the standard block buffer cache. Range of values: At least 16 MB. Default value: 48 MB. The DB_FILE_MULTIBLOCK_READ_COUNT parameter specifies the maximum number of blocks read during an input/output (I/O) operation involving a full sequential scan. Range of values: Operating system dependent. Default value: OS dependent. The DB_FILES parameter specifies the maximum number of database files that can be opened for this database. Range of values: MAXDATAFILES – OS dependent. Default to se value: OS dependent (200 on Solaris). n ice l The PGA_AGGREGATE_TARGET parameter specifies the amount of Program Global bleSet this Area (PGA) memory allocated to all server processes attached to the instance. fera areas. This parameter to a positive value before enabling the automatic settings working n of -tradatabase uses this memory does not reside in the System Global Area (SGA). The non setting this parameter, parameter as a target amount of PGA memory to use. When. s a de asystem iavailable to the Oracle instance. subtract the SGA from the total memory on the ) h t Gu The remaining memory can be assignedm PGA_AGGREGATE_MEMORY. Range of to co den il.G totspecify this limit in kilobytes, megabytes, or values: Integers plus letter K, M, or a Su gm MB and maximum value is 4096 GB. Default: 10 MB or gigabytes. Minimum value is 10 is @ th 20% of the size ofugg the SGA, whichever is greater. use ah parameter specifies the maximum number of OS user processes that can The PROCESSES g (z connect to an Oracle server. This value should allow for all background n simultaneously zha Range of values: 6 to an OS-dependent value. Default value: OS dependent. processes. nhuThe SHARED_POOL_SIZE parameter specifies the size of the shared pool in bytes. The xi shared pool contains objects such as shared cursors, stored procedures, control structures, and parallel execution message buffers. Larger values can improve performance in multiuser systems. Range of values: The size of a granule–OS dependent. Default value: If 64 bit, then 64 MB, or else 16 MB. The UNDO_MANAGEMENT parameter specifies which undo space management mode the system should use. When set to AUTO, the instance is started in System Managed Undo (SMU) mode. Otherwise, it is started in Rollback Undo (RBU) mode. In RBU mode, undo space is allocated externally as rollback segments. In SMU mode, undo space is allocated externally as undo tablespaces. Range of values: AUTO or MANUAL. Default value: If the UNDO_MANAGEMENT parameter is omitted when the first instance is started, the default value of MANUAL is used and the instance is started in RBU mode. If it is not the first instance, the instance is started in the same undo mode as all other existing instances.Unauthorized reproduction or distribution prohibited. Copyright© 2008, Oracle and/or its affiliates.Oracle Database 10g: Administration Workshop I 4 - 17Viewing and Modifying Initialization Parametersg Viewing and Modifying Initialization Parameters han use Enterprise Manager to view and modify initialization parameters by clicking z can huYouInitialization Parameters in the Database Configuration region of the Database xin All Administration tabbed page.tr ona n e. has uid ) om ent G c ail. Stud m i @gCopyrights 2008, Oracle. All rights reserved. gg se th © u u zah (e nsf arl ble aicnse etoUnauthorized reproduction or distribution prohibited. Copyright© 2008, Oracle and/or its affiliates.Oracle Database 10g: Administration Workshop I 4 - 18Database Startup and ShutdownComponents SQL*Plus Init Params > DB Startup DB Shutdown Alert Log Perf ViewsorDatabase Startup and Shutdown ng hayou click either startup or shutdown, you are prompted for credentials that are used z When hufor both logging on to the host (the computer on which the database resides) and logging in xin to the database itself. Enter the credentials. You can then click Advanced Options to change any startup options or shutdown mode, as needed. Also, you can click Show SQL to see the SQL statements that are used for the startup or shutdown.tr ona n e. has uid ) om ent G c ail. Stud m i @gCopyrights 2008, Oracle. All rights reserved. gg se th © u u zah (e nsf arl ble aicnse etoUnauthorized reproduction or distribution prohibited. Copyright© 2008, Oracle and/or its affiliates.Oracle Database 10g: Administration Workshop I 4 - 19Starting Up an Oracle Database InstanceStarting Up an Oracle Database Instance ng hadatabase is currently not started when you go to the Enterprise Manager Database Ifz the huControl page, click Startup to perform the startup. Enter the host credentials and, n xi optionally, choose the startup mode.tr ona n e. has uid ) om ent G c ail. Stud m i @gCopyrights 2008, Oracle. All rights reserved. gg se th © u u zah (e nsf arl ble aicnse etoUnauthorized reproduction or distribution prohibited. Copyright© 2008, Oracle and/or its affiliates.Oracle Database 10g: Administration Workshop I 4 - 20Starting Up an Oracle Database Instance: NOMOUNTOPEN STARTUP MOUNTNOMOUNT Instance startedSHUTDOWNz in which huWhen starting the database instance, select the stateinstance. it starts. The following n scenarios describe different stages of starting up an xi An instance is typically started only in NOMOUNT mode during database creation, during re-creation of control files, or during certain backup and recovery scenarios. Starting an instance includes the following tasks: • Searching <oracle_home>/dbs for a file of a particular name in this order: - spfile<SID>.ora - If not found, spfile.ora - If not found, init<SID>.ora This is the file that contains initialization parameters for the instance. Specifying the PFILE parameter with STARTUP overrides the default behavior. • Allocating the SGA • Starting the background processes • Opening the alert<SID>.log file and the trace files Note: SID is the system ID, which identifies the instance (for example, ORCL).Unauthorized reproduction or distribution prohibited. Copyright© 2008, Oracle and/or its affiliates.Oracle Database 10g: Administration Workshop I 4 - 21Starting Up an Oracle Database Instance: NOMOUNT nghatr ona n e. has uid ) om ent G c ail. Stud m i @gCopyrights 2008, Oracle. All rights reserved. gg se th © u u zah (e nsf arl ble aicnse etoStarting Up an Oracle Database Instance: MOUNTOPEN STARTUP MOUNT Control file opened for this instanceNOMOUNT Instance startedSHUTDOWNz huMounting a database includes the following tasks: instance xin • Associating a database with a previously started • Locating and opening the control files specified in the parameter file • Reading the control files to obtain the names and statuses of the data files and online redo log files. However, no checks are performed to verify the existence of the data files and online redo log files at this time. To perform specific maintenance operations, start an instance and mount a database, but do not open the database. For example, the database must be mounted but must not be opened during the following tasks: • Renaming data files (Data files for an offline tablespace can be renamed when the database is open.) • Enabling and disabling online redo log file archiving options • Performing full database recovery Note: A database may be left in MOUNT mode even though an OPEN request has been made. This may be because the database needs to be recovered in some way.Unauthorized reproduction or distribution prohibited. Copyright© 2008, Oracle and/or its affiliates.Oracle Database 10g: Administration Workshop I 4 - 22Starting Up an Oracle Database Instance: MOUNT nghatr ona n e. has uid ) om ent G c ail. Stud m i @gCopyrights 2008, Oracle. All rights reserved. gg se th © u u zah (e nsf arl ble aicnse eto。

sql 第四范式-概述说明以及解释1.引言1.1 概述第四范式是关系数据库设计中的一个重要概念，它是指在数据库设计中，将非主属性间的关系通过引入新的实体进行拆分，达到消除数据冗余和提高数据完整性的目的。

本文将围绕第四范式展开讨论，并探讨其在实际应用中的挑战。

在传统关系数据库设计中，我们常常会遇到冗余数据的问题。

冗余数据不仅浪费了存储空间，还容易导致数据的不一致性和更新异常。

为了解决这个问题，提出了规范化的概念，其中第四范式就是规范化的最高级别。

第四范式要求数据库中每个非主属性都完全依赖于键，并且不存在非主属性之间的传递依赖。

换句话说，第四范式要求数据库中的每个非主属性都是直接依赖于键的，而不是间接依赖于其他非主属性。

第四范式的优点是显而易见的。

首先，它能够消除数据冗余，减少存储空间的占用。

其次，由于数据的一致性得到了保证，更新异常的风险也大大降低。

此外，第四范式还能够提高查询的效率，因为数据的拆分使得数据的访问更加快速和高效。

然而，第四范式在实际应用中也会面临一些挑战。

首先，拆分数据可能导致查询的复杂性增加。

由于数据被分散存储在不同的表中，查询的时候需要进行多次联结操作，增加了查询的成本。

其次，第四范式对于数据一致性的要求较高，需要在应用层面进行更加复杂的控制和约束，这可能带来额外的开发和维护成本。

最后，第四范式需要根据具体业务需求进行合理的实体拆分，这对于数据库设计师来说可能是一项具有挑战性的任务。

综上所述，第四范式是关系数据库设计中一个重要的概念，它可以消除数据冗余、提高数据完整性和查询效率。

然而，在实际应用中，我们需要权衡其优点和挑战，并根据具体业务需求进行合理的设计和实施。

在下文中，我们将详细探讨第四范式的相关概念和优点，以及在实践中可能遇到的挑战。

1.2文章结构1.2 文章结构本文将按照以下结构展开讨论第四范式的相关内容：1. 引言：首先，我们会对整篇文章进行一个概述，明确我们要讨论的问题和目的，引起读者对文章的兴趣。

数据库设计的范式与原则数据库设计是构建一个关系型数据库系统的基础步骤，良好的数据库设计可以提高数据管理的效率和数据质量。

在进行数据库设计时，我们需要遵循范式与原则来保证数据库的稳定性和一致性。

本文将介绍数据库设计的范式与原则，并探讨它们在实际应用中的作用。

一、数据库设计的范式范式是数据库中数据组织和存储规范的标准，包括了一系列规则和要求，以减少冗余数据并确保数据库的一致性。

数据库设计中常用的范式包括第一范式（1NF）、第二范式（2NF）、第三范式（3NF）等，每个范式都建立在前一个范式的基础上，层层递进。

1. 第一范式（1NF）第一范式要求数据库中的每个字段都是原子性的，即不可再分。

它消除了重复数据和数组属性，确保数据的唯一性和一致性。

2. 第二范式（2NF）第二范式要求数据库表中的每个非主键字段完全依赖于主键。

通过将非主键字段与主键字段关联，可以消除部分冗余数据，提高数据存储效率。

3. 第三范式（3NF）第三范式要求数据库表中的每个非主键字段不依赖于其他非主键字段。

通过进一步消除数据的冗余性，可以提高数据库的稳定性和一致性。

二、数据库设计的原则除了范式之外，数据库设计还需要遵循一些原则，以提高数据库的可扩展性和性能。

1. 实体完整性原则实体完整性原则要求数据库中的每个实体都应该有一个唯一的标识符，通常是一个主键。

这样可以确保数据的唯一性和一致性。

2. 关系完整性原则关系完整性原则要求数据库表之间的关系必须是有效且可靠的，通常使用外键来实现。

通过定义外键关系，可以确保数据的准确性和一致性。

3. 数据冗余原则数据冗余原则要求尽量避免数据的冗余存储，以减少存储空间的占用，并提高数据的查询效率。

通过合理设计数据库表的结构和关系，可以最大限度地减少数据冗余。

4. 性能优化原则性能优化原则要求在数据库设计中考虑到数据的访问和查询效率。

通过合理设计索引、分区等优化手段，可以提高数据库的读写性能，减少查询时间和资源消耗。

数据库设计的范式数据库设计是构建一个高效、可靠和易于维护的数据库的关键步骤。

范式是一种规范，用于指导数据库设计的过程，旨在消除冗余数据以及数据的不一致性。

在本文中，我将介绍数据库设计的范式，并逐步解释如何根据范式进行数据库设计。

第一范式（1NF）：确保每个数据库表都是原子的在第一范式中，每个数据库表都应该是原子的，即每个表中的列都应该是不可再分的。

例如，如果我们正在设计一个学生表，那么每个学生应该有自己的行，并且每行应该只包含关于该学生的信息，例如姓名、学号和联系方式等。

这样可以避免冗余数据的存在。

第二范式（2NF）：确保表中的每列都与主键直接相关在第二范式中，每个表应该满足第一范式的要求，并且每列都应该与主键直接相关。

例如，如果我们有一个课程表和一个成绩表，那么成绩表中的每个列应该与课程表的主键直接相关。

这样可以确保数据的一致性和完整性。

第三范式（3NF）：确保表中的每列都与主键之间不存在传递依赖关系在第三范式中，每个表应该满足第二范式的要求，并且表中的每列都应该与主键之间不存在传递依赖关系。

传递依赖关系指的是当一个非主键列依赖于另一个非主键列时，存在依赖关系。

为了避免传递依赖关系，我们可以将依赖关系迁移到一个新的表中。

例如，如果我们有一个订单表，其中包含订单号、产品名称和产品价格等列，那么产品价格列应该与产品名称列存在传递依赖关系。

为了满足第三范式，我们可以将产品价格迁移到一个新的产品表中，并与产品名称列相关联。

总结：数据库设计的范式是一种规范，用于指导数据库设计过程。

其中，第一范式确保每个表都是原子的，第二范式确保每个列与主键直接相关，第三范式确保每列与主键之间不存在传递依赖关系。

通过遵循这些范式，我们可以构建高效、可靠和易于维护的数据库。

数据库设计基础知识数据库是现代信息系统中的关键组成部分，它存储和管理着大量的数据。

数据库设计是建立和组织数据库的过程，它决定了数据库的结构和功能。

本文将介绍数据库设计的基础知识，包括数据库范式、关系模型、实体-关系图和SQL语言等。

一、数据库范式数据库范式是指数据库中数据的组织方式和关系。

它是根据数据的依赖关系分为不同的级别。

1. 第一范式（1NF）：确保每个属性都是原子的，即不可再分。

每个属性都应该具有唯一的名称，不会存在重复的属性。

2. 第二范式（2NF）：确保非主键属性完全依赖于主键。

换句话说，非主键属性应该与主键属性直接相关，而非间接依赖。

3. 第三范式（3NF）：确保非主键属性之间没有传递依赖关系。

每个非主键属性应该与主键或其他非主键属性直接相关，而不是依赖于其他非主键属性。

二、关系模型关系模型是一种用来表示数据库结构的概念模型。

它采用表格的形式，每个表格代表一个实体，每个实体具有唯一的标识符（主键）和属性。

1. 实体：在关系模型中，实体表示现实世界中的对象或事物，如学生、教师或订单等。

每个实体都有唯一的标识符（主键）和属性。

2. 属性：属性是实体的特征或描述，如学生的姓名、年龄或成绩等。

在关系模型中，属性以列的形式存储在表格中。

3. 关系：关系是实体之间的联系，它可以通过共享相同的属性值来建立。

在关系模型中，关系通过外键来表示。

三、实体-关系图实体-关系图（ER图）是一种用来表示关系模型的图形符号。

它以实体、属性和关系为基础，使用图形和符号来表示它们之间的联系。

1. 实体框：实体框表示一个实体，在框内写上实体的名称。

2. 属性：属性用椭圆形表示，写在相应实体框的下方。

3. 关系线：关系线表示实体之间的联系，它可以是一对一、一对多或多对多的关系。

关系线可以用普通线条或菱形表示。

四、SQL语言SQL（结构化查询语言）是一种用来管理和操纵数据库的标准语言。

它可以执行查询、插入、更新和删除操作，通过语句与数据库进行交互。

数据库第四范式第四范式是数据库设计中的一种规范，它强调了数据表中存在的多个关系之间的独立性。

该规范建议将一张数据表中的多个属性拆分成多个独立的表，以避免数据冗余和数据不一致的发生。

本文将介绍数据库第四范式的概念、目的、实现方法和其对数据库性能的影响。

1.概念数据库第四范式又称偏函数依赖范式，是对第三范式的进一步完善和提高。

第四范式规定的是任何一个非主属性（即不属于关系主键）都不能由部分主属性函数决定。

否则就需要将该属性单独拆分出来，构成一个新的关系。

2.目的使用第四范式可以避免数据冗余和数据不一致的发生。

例如，当一张数据表中包含了多个实体的属性时，可能会导致某些数据在多个记录中出现，这样会占用过多的存储空间，并且更新数据时可能会导致数据不一致。

而将这些属性拆分到独立的数据表中，可以减少数据冗余，并使得每张表只包含一个实体的属性，从而提高数据的一致性和可靠性。

3.实现方法实现第四范式需要进行逐一分析和整理数据表中的属性，将其拆分成多个独立的数据表。

在这个过程中，需要特别注意以下两点：（1）确定主键：每个新的数据表都需要定义一个主键，以保证数据的唯一性。

主键可以由单个属性或多个属性构成。

（2）确保数据的完整性：当数据被拆分成多个数据表后，需要通过引入外键来保持数据表之间的联系。

在这个过程中，需要确保数据的完整性，即每条记录的外键值都对应被引用表的主键值。

4.对数据库性能的影响数据库第四范式可以提高数据表的一致性和可靠性，但它也会带来性能上的损失。

因为在使用第四范式后，需要通过联结操作来获取相关的数据，这可能会导致查询的速度变慢。

同时，数据表之间的关系越复杂，联结操作的次数也会越多，对性能的影响也会越大。

因此，在设计数据库时需要在保持数据一致性的前提下，尽量减少数据表之间的复杂关系，以提高数据库的查询速度和性能。

综上所述，数据库第四范式是一种遵循最小化数据冗余的规范，它可以提高数据表的一致性和可靠性，但也会带来性能上的损失。

数据库设计范式数据库设计范式是指在关系数据库中，通过一定的规则和标准来设计和组织数据库表结构，以保证数据的一致性、完整性和可靠性。

在数据库设计中，范式分为一至六个级别，依次递增，每个级别都有特定的规则和要求。

本文将介绍和讨论数据库设计范式的概念、各个级别的要求和特点。

一、第一范式（1NF）第一范式是数据库设计的最基本要求，它要求数据库中的每个属性具有原子性，即属性不能再分解为更小的单元。

这意味着每个属性的值都是不可再分的简单类型，不可再细分的部分。

这样可以避免数据冗余和重复，提高数据的存储效率和查询效率。

二、第二范式（2NF）第二范式要求数据库中的每个非主属性都要完全依赖于主键，而不能依赖于主键的一部分。

也就是说，表中的每个属性都必须与完整的候选键相关，而不是部分相关。

这样可以消除非主属性之间的冗余和数据依赖关系，提高数据库的数据一致性和查询性能。

三、第三范式（3NF）第三范式要求数据库中的每个非主属性都不传递依赖于主键，即非主属性之间不能相互依赖。

如果一个非主属性既依赖于主键，又依赖于另一个非主属性，就会造成数据冗余和更新异常。

通过将这种依赖关系分解成独立的关系表，可以消除冗余、提高数据的一致性和查询性能。

四、BC范式（BCNF）BC范式是在第三范式的基础上引入了关键依赖的概念。

关键依赖是指在一个关系表中，如果存在A->B的函数依赖，其中B不是候选键的一部分，那么称关系表不满足BC范式。

为了消除关键依赖，可以将关系表进行拆分，建立新的关系表，以保证数据的一致性和更新效率。

五、第四范式（4NF）第四范式要求数据库中的每个多值依赖都要通过分解，以避免数据冗余和更新异常。

多值依赖是指当一个关系表中存在多个多值属性时，这些属性之间的依赖关系。

通过拆分多值属性和建立新的关系表，可以提高数据库的数据一致性和查询性能。

六、第五范式（5NF）第五范式（又称完美范式）是在第四范式的基础上引入了连接依赖的概念。