sql语句练习:找出平均工资小于5000的商店所在的城市

员工信息表 employee： user_id , name, store_id, salary

商店表stores：store_id, name,city

参考答案：select a.city from stores a,employee b where b.store_id=a.store_id group by b.store_id having avg(b.salary)<5000