join练习

最新推荐文章于 2024-07-12 10:36:10 发布

claudxyz

最新推荐文章于 2024-07-12 10:36:10 发布

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分类专栏： oracle学习文章标签： join

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本文详细介绍了SQL中不同类型的连接操作，包括普通自然连接、使用using指定相同字段的连接、使用on指定不同字段名称但意义相同的连接，以及左连接、右连接和全连接的具体实现方式。

1、select a.operatorid,a.operatorname,b.orgname from sys_employee a natural join sys_organization b

普通自然连接

2、select a.operatorid,a.operatorname,b.orgname from sys_employee a join sys_organization b using (orgid)

如果出现多个相同对应的字段使用using

3、select a.operatorid,a.operatorname,b.orgname from sys_employee a join sys_organization b
on a.orgid = b.orgid and a.operatorname = 'xx'

如果相对应的字段名不一致使用on

4、select a.operatorid,a.operatorname,b.orgname from sys_employee a left join sys_organization b
on a.orgid = b.orgid and a.operatorname = 'xx'

左连接

5、select a.operatorid,a.operatorname,b.orgname from sys_employee a right join sys_organization b
on a.orgid = b.orgid and a.operatorname = 'xx'

右连接

6、select a.operatorid,a.operatorname,b.orgname from sys_employee a full join sys_organization b
on a.orgid = b.orgid and a.operatorname = 'xx'

全连接