一、简介

记录一下模糊查询 分组查询以及子查询的使用

二、使用

假设有数据库中员工表employee(e_id,e_name,d_id,e_salary) 和部门表department(d_id,d_name),

2.1 分组查询 GROUP BY  

按部门分组,筛选条件为部门平均工资大于7000

SELECT d_id AS '部门编号', AVG(e_salary) AS '部门平均工资' FROM employee
GROUP BY d_id 
HAVING AVG(e_salary) > 7000

2.2 模糊查询 LIKE

查询部门中，姓王的员工

SELECT * FROM employee 
WHERE LIKE '王%'

2.3 子查询

查找部门编号最小的员工信息

SELECT * FROM employee 
WHERE d_id = (SELECT MIN(d_id) FROM department)