自连接可以看成内连接的一种，只是连接的表是自身而已 子查询版本 ~~~ SELECT name FROM employee WHERE department = ( SELECT department FROM employee WHERE name = "Jim"); ~~~ 自连接版本 ~~~ SELECT e1.name FROM employee AS e1 INNER JOIN employee AS e2 ON e1.department = e2.department AND e2.name = "Jim"; ~~~