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mysql 错题集

作者：互联网

1.查询各部门中工资比本部门平均工资高的员工的员工号,姓名和工资

①查询各部门的平均工资

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

在这里插入图片描述

②连接①结果集和employees表,进行筛选

SELECT employee_id,last_name,salary,e.department_id
FROM employees e
INNER JOIN (
	SELECT AVG(salary) ag ,department_id
	FROM employees
	GROUP BY department_id
)ag_dep
ON e.`department_id` = ag_dep.department_id
WHERE salary > ag;

我们把①中的结果集看成一个新表,新表有两列,一列是department_id,一列是平均工资.然后让这个新表与employees连接,连接条件就是department_id,然后根据employees表匹配信息,如果不加上e.salary>ag_dep.salary.

标签：salary,ag,employees,错题,mysql,department,id,SELECT
来源： https://blog.csdn.net/m0_49089924/article/details/120253564