首先看看Left Join 与Right Join 与 Inner Join 与 Full Join对表进行操作后得到的结果。
在数据库中新建两张表，并插入要测试的数据。新建表：
[sql] view plain copy print ? USE [Test] GO /****** 对象: Table [dbo].[EMP] 脚本日期: 06/22/2012 15:37:28 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[EMP]( [ENAME] [nchar](10) COLLATE Chinese_PRC_CI_AS NOT NULL, [CITY] [nchar](10) COLLATE Chinese_PRC_CI_AS NULL ) ON [PRIMARY] USE [Test] GO /****** 对象: Table [dbo].[EMP] 脚本日期: 06/22/2012 15:37:28 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[EMP]( [ENAME] [nchar](10) COLLATE Chinese_PRC_CI_AS NOT NULL, [CITY] [nchar](10) COLLATE Chinese_PRC_CI_AS NULL ) ON [PRIMARY][sql] view plain copy print ? USE [Test] GO /****** 对象: Table [dbo].[SAL] 脚本日期: 06/22/2012 15:38:04 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[SAL]( [ENAME] [nchar](10) COLLATE Chinese_PRC_CI_AS NOT NULL, [SALARY] [money] NULL ) ON [PRIMARY] USE [Test] GO /****** 对象: Table [dbo].[SAL] 脚本日期: 06/22/2012 15:38:04 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[SAL]( [ENAME] [nchar](10) COLLATE Chinese_PRC_CI_AS NOT NULL, [SALARY] [money] NULL ) ON [PRIMARY]
插入数据得到的表：
EMP表：
SAL表：
左连接 [sql] view plain copy print ? select * from EMP Left join SAL on EMP.ENAME = SAL.ENAME; select * from EMP Left join SAL on EMP.ENAME = SAL.ENAME; 左连接，表EMP是主表，因此查询结果是显示EMP（主表）的全部信息和SAL（附表）与EMP相关的信息。右连接 [sql] view plain copy print ? Select * from EMP Right join SAL on EMP.ENAME = SAL.ENAME; Select * from EMP Right join SAL on EMP.ENAME = SAL.ENAME; 右连接，表SAL是主表，因此查询结果显示SALT（主表）的全部信息和EMP(附表)与SAL想关的信息。内连接 [sql] view plain copy print ? SELECT * FROM EMP inner join SAL on EMP.ENAME = SAL.ENAME; SELECT * FROM EMP inner join SAL on EMP.ENAME = SAL.ENAME; 内连接，显示的是连个表相关的信息。全连接 [sql] view plain copy print ? SELECT * FROM EMP full join SAL on EMP.ENAME = SAL.ENAME; SELECT * FROM EMP full join SAL on EMP.ENAME = SAL.ENAME; 全连接，显示两个表所有的信息。