mysql七种常用的JOIN查询

1 A、B两表共有

select * from tbl_emp a inner join tbl_dept b on a.deptId = b.id;

 

2 A、B两表共有+A的独有

select * from tbl_emp a left join tbl_dept b on a.deptId = b.id;

 

3 A、B两表共有+B的独有

select * from tbl_emp a right join tbl_dept b on a.deptId = b.id;

 

4 A的独有

select * from tbl_emp a left join tbl_dept b on a.deptId = b.id where b.id is null;

 

5 B的独有

select * from tbl_emp a right join tbl_dept b on a.deptId = b.id where a.deptId is null; #B的独有

 

6 AB全有

#MySQL Full Join的实现 因为MySQL不支持FULL JOIN,下面是替代方法

#left join + union(可去除重复数据)+ right join

SELECT * FROM tbl_emp A LEFT JOIN tbl_dept B ON A.deptId = B.id

UNION

SELECT * FROM tbl_emp A RIGHT JOIN tbl_dept B ON A.deptId = B.id

 

7 A的独有+B的独有

SELECT * FROM tbl_emp A LEFT JOIN tbl_dept B ON A.deptId = B.id WHERE B.`id` IS NULL

UNION

SELECT * FROM tbl_emp A RIGHT JOIN tbl_dept B ON A.deptId = B.id WHERE A.`deptId` IS NULL;