SQL22 - 统计各个部门的工资记录数

题目描述：

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

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`));

 

题目描述：

中等

 

解答：

select departments.dept_no,departments.dept_name,count(salaries.salary)
from departments left join dept_emp
on departments.dept_no = dept_emp.dept_no
left join salaries
on dept_emp.emp_no = salaries.emp_no
group by departments.dept_no,departments.dept_name