MySQL笔记

MySQL中select语句嵌套使用

例题：查询最低工资大于50号部门最低工资的部门id和其最低工资

思考角度：

1. 查询50号部门的最低工资

   select min(salary) from employees where department_id = 50;

1. 查询每个部门的最低工资

   select min(salary), department_id
   from employees group by department_id;

1. 在2的基础上，筛选满足min(salary) > 1

   select min(salary), department_id
   from employees group by department_id
   having min(salary) > (select min(salary) from employees where department_id = 50);

连接语句

分类

左外连接，右外连接，内连接，全连接

示意图