分组过滤查询

语法：SELECT 列名 FROM 表名 WHERE 条件 GROUP BY 分组列 HAVING 过滤规则

# 统计60、70、80号部门的最高工资
# 思路：先拿到所有部门的最高工资
# 再筛选出指定部门
SELECT MAX(salary), department_id
FROM t_employees
GROUP BY department_id
HAVING department_id in (60, 70, 80);