【牛客SQL】SQL22 统计各个部门的工资记录数

题目描述

描述 有一个部门表departments简况如下:

有一个，部门员工关系表dept_emp简况如下:

有一个薪水表salaries简况如下:

请你统计各个部门的工资记录数，给出部门编码dept_no、部门名称dept_name以及部门在salaries表里面有多少条记录sum，按照dept_no升序排序，以上例子输出如下:

示例1
输入：
drop table if exists  `departments` ; 
drop table if exists  `dept_emp` ; 
drop table if exists  `salaries` ; 
CREATE TABLE `departments` (
`dept_no` char(4) NOT NULL,
`dept_name` varchar(40) NOT NULL,
PRIMARY KEY (`dept_no`));
CREATE TABLE `dept_emp` (
`emp_no` int(11) NOT NULL,
`dept_no` char(4) NOT NULL,
`from_date` date NOT NULL,
`to_date` date NOT NULL,
PRIMARY KEY (`emp_no`,`dept_no`));
CREATE TABLE `salaries` (
`emp_no` int(11) NOT NULL,
`salary` int(11) NOT NULL,
`from_date` date NOT NULL,
`to_date` date NOT NULL,
PRIMARY KEY (`emp_no`,`from_date`));
INSERT INTO departments VALUES('d001','Marketing');
INSERT INTO departments VALUES('d002','Finance');
INSERT INTO dept_emp VALUES(10001,'d001','2001-06-22','9999-01-01');
INSERT INTO dept_emp VALUES(10002,'d001','1996-08-03','9999-01-01');
INSERT INTO dept_emp VALUES(10003,'d002','1996-08-03','9999-01-01');
INSERT INTO salaries VALUES(10001,85097,'2001-06-22','2002-06-22');
INSERT INTO salaries VALUES(10001,88958,'2002-06-22','9999-01-01');
INSERT INTO salaries VALUES(10002,72527,'1996-08-03','9999-01-01');
INSERT INTO salaries VALUES(10003,32323,'1996-08-03','9999-01-01');
复制
输出：
d001|Marketing|3
d002|Finance|1

题解

运行时间：13ms 超过80.58% 用Sqlite提交的代码 占用内存：3456KB 超过17.53%用Sqlite提交的代码

SELECT d1.dept_no, d1.dept_name, COUNT(d1.dept_no)
FROM departments AS d1 JOIN (
    SELECT s.emp_no, d2.dept_no 
    FROM dept_emp AS d2 JOIN salaries AS s
    ON d2.emp_no = s.emp_no
) AS t
ON d1.dept_no = t.dept_no
GROUP BY d1.dept_no
;