MySQL 七种 JOIN

标签：select   mysql   union   rom   pre   sele   mys   inner   dep   

SELECT
    *
FROM
    t_dept a
INNER JOIN t_emp b ON a.id = b.deptId;

左独占+共有

SELECT
    *
FROM
    t_dept a
LEFT JOIN t_emp b ON a.id = b.deptId;

右独占+共有

SELECT
    *
FROM
    t_dept a
RIGHT JOIN t_emp b ON a.id = b.deptId;

左独占

SELECT
    *
FROM
    t_dept a
LEFT JOIN t_emp b ON a.id = b.deptId
WHERE b.deptId IS NULL;

右独占

SELECT
    *
FROM
    t_dept a
RIGHT JOIN t_emp b ON a.id = b.deptId
WHERE a.id IS NULL;

左右全部

SELECT
    *
FROM
    t_dept a
LEFT JOIN t_emp b ON a.id = b.deptId
UNION
SELECT
    *
FROM
    t_dept a
RIGHT JOIN t_emp b ON a.id = b.deptId;

左独占+右独占

SELECT
    *
FROM
    t_dept a
LEFT JOIN t_emp b ON a.id = b.deptId
WHERE b.deptId IS NULL 
UNION
SELECT
    *
FROM
    t_dept a
RIGHT JOIN t_emp b ON a.id = b.deptId
WHERE a.id IS NULL;

MySQL 七种 JOIN

标签：select   mysql   union   rom   pre   sele   mys   inner   dep   

原文地址：https://blog.51cto.com/13559120/2504351