mysql 7种JOIN理论，看完你就懂了

张铎（信念）

于 2021-08-09 08:53:34 发布

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分类专栏：数据库文章标签： mysql

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

select * from tbl_emp a LEFT JOIN tbl_dept b on a.deptId=b.id;

select * from tbl_emp a RIGHT JOIN tbl_dept b on a.deptId=b.id;

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

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

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;

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.id is null;