mysql七種常用的JOIN查詢

1 A、B兩表共有

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

2 A、B兩表共有+A的獨有

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

3 A、B兩表共有+B的獨有

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

4 A的獨有

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

5 B的獨有

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

6 AB全有

#MySQL Full Join的實現 因為MySQL不支持FULL JOIN,下面是替代方法

#left join + union(可去除重復數據)+ 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的獨有+B的獨有

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;