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 plaincopyprint? USE[Test]GO/******对象:Table[dbo].[EMP]脚本日期:06/22/15:37:28******/SETANSI_NULLSONGOSETQUOTED_IDENTIFIERONGOCREATETABLE[dbo].[EMP]([ENAME][nchar](10)COLLATEChinese_PRC_CI_ASNOTNULL,[CITY][nchar](10)COLLATEChinese_PRC_CI_ASNULL)ON[PRIMARY]
USE [Test]GO/****** 对象: Table [dbo].[EMP] 脚本日期: 06/22/ 15:37:28 ******/SET ANSI_NULLS ONGOSET QUOTED_IDENTIFIER ONGOCREATE 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 plaincopyprint? USE[Test]GO/******对象:Table[dbo].[SAL]脚本日期:06/22/15:38:04******/SETANSI_NULLSONGOSETQUOTED_IDENTIFIERONGOCREATETABLE[dbo].[SAL]([ENAME][nchar](10)COLLATEChinese_PRC_CI_ASNOTNULL,[SALARY][money]NULL)ON[PRIMARY]
USE [Test]GO/****** 对象: Table [dbo].[SAL] 脚本日期: 06/22/ 15:38:04 ******/SET ANSI_NULLS ONGOSET QUOTED_IDENTIFIER ONGOCREATE 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 plaincopyprint? select*fromEMPLeftjoinSALonEMP.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 plaincopyprint? Select*fromEMPRightjoinSALonEMP.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 plaincopyprint? SELECT*FROMEMPinnerjoinSALonEMP.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 plaincopyprint? SELECT*FROMEMPfulljoinSALonEMP.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。