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数据库-----catalog与schema简介

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Jun 07, 2016 pm 04:10 PM

sqldatabaseIntroduction

在SQL环境下Catalog和Schema都属于抽象概念，主要用来解决命名冲突问题一个数据库系统包含多个Catalog，每个Catalog包含多个Schema，每个Schema包含多个数据库对象（表、视图、字段等）如数据库对象表的全限定名可表示为：Catalog名.Schema名.表名ＳＱＬ

在SQL环境下Catalog和Schema都属于抽象概念，主要用来解决命名冲突问题

一个数据库系统包含多个Catalog，每个Catalog包含多个Schema，每个Schema包含多个数据库对象（表、视图、字段等）

如数据库对象表的全限定名可表示为：Catalog名.Schema名.表名

ＳＱＬ标准并不要求每个数据库对象的完全限定名称是唯一的，就象域名一样，如果喜欢的话，每个ＩＰ地址都可以拥有多个域名

从实现的角度来看，各种数据库系统对Catalog和Schema的支持和实现方式千差万别，比较简单而常用的实现方式是使用数据库名作为Catalog名，使用用户名作为Schema名，具体可参见下表：

供应商	Catalog支持	Schema支持
Oracle	不支持	Oracle User ID
MySQL	不支持	数据库名
MS SQL Server	数据库名	对象属主名，2005版开始有变
DB2	指定数据库对象时，Catalog部分省略	Catalog属主名
Sybase	数据库名	数据库属主名
Informix	不支持	不需要
PointBase	不支持	数据库名

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