标签:not employees _id 案例 length esc 多个 order by avg
按表达式或函数分组:#案例:按员工的姓名的长度分组,查询每一组的员工个数,筛选员工个数大于五
SELECT
COUNT(*),LENGTH(last_name)
FROM
employees
GROUP BY
LENGTH(last_name)
HAVING
COUNT(*)>5;
按多个字段分组:
#案例:查询每个部门每个工种的员工的平均工资
SELECT
AVG(salary),department_id,job_id
FROM
employees
GROUP BY
department_id,job_id;
排序
#案例:查询每个部门每个工种的部门编号不为null的员工的平均工资>10000,并且按平均工资的高低显示
SELECT
AVG(salary),department_id,job_id
FROM
employees
WHERE
department_id IS NOT NULL
GROUP BY
department_id,job_id
HAVING
AVG(salary)>10000
ORDER BY
AVG(salary) DESC;
标签:not employees _id 案例 length esc 多个 order by avg
原文地址:https://blog.51cto.com/14437184/2436653