统计各个部门对应员工涨幅的次数总和

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` ));

select dept_no,dept_name,sum(sum) sum from (select emp_no,d.dept_no,dept_name from dept_emp de left join departments d on de.dept_no = d.dept_no) info inner join (select emp_no,count(salary) sum from salaries s group by emp_no) s on info.emp_no = s.emp_no group by dept_no

-- 涨幅次数总和
(select emp_no,count(salary) sum from salaries s group by emp_no) s

-- 部门信息
(select emp_no,d.dept_no,dept_name from dept_emp de left join departments d on de.dept_no = d.dept_no) info