题目：找出高于所在部门平均工资的员工的姓名，工资，所在部门的编号，部门的平均工资

1、首先找出每个部门的平均工资

SELECT AVG(salary) pjgz,did FROM man WHERE GROUP BY did

2、将其作为临时表，放到主查询中

SELECT man.name ,man.salary ,lsb.did ,lsb.pjgz FROM man ,(SELECT AVG(salary) pjgz,did FROM man GROUP BY did) lsb WHERE man.did =lsb.did AND man.salary > lsb.pjgz;