mysql 筛选后分组查询

语法:
select 分组函数，列（要求出现在group by的后面）
from 表
where ..
group by 分组的列表
order by ...

#案例：查询各个部门的平均工资

SELECT AVG(salary),department_id FROM employees GROUP BY     department_id ORDER BY     department_id DESC;

#案例:查询每个工种的最高工资

SELECT     MAX(salary),job_id FROM     employees GROUP BY     job_id;

#案例:查询每个部门的位置个数

SELECT     COUNT(location_id),department_name FROM     departments GROUP BY     department_name;

#案例:查询邮箱中包含a字符的，每个部门的平均工资

SELECT     AVG(salary),department_id FROM     employees WHERE     email LIKE('%a%') GROUP BY     department_id;

#案例：查询有奖金的每个领导手下员工的最高工资

SELECT     MAX(salary),manager_id FROM      employees WHERE     commission_pct IS NOT NULL GROUP BY      manager_id;

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来源：51CTO

作者：wx5d21d5e6e5ab1

链接：https://blog.51cto.com/14437184/2436585