获取员工其当前的薪水比其manager当前薪水还高的相关信息,当前表示to_date='9999-01-01',
结果第一列给出员工的emp_no,
第二列给出其manager的manager_no,
第三列给出该员工当前的薪水emp_salary,
第四列给该员工对应的manager当前的薪水manager_salary
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 `dept_manager` (
`dept_no` char(4) NOT NULL,
`emp_no` int(11) 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`));
解决思路
SELECT sem.emp_no emp_no, sdm.emp_no manager_no, sem.salary emp_salary,sdm.salary manager_salary
FROM (SELECT s.salary, s.emp_no, de.dept_no
FROM salaries s
INNER JOIN dept_emp de
ON s.emp_no = de.emp_no
AND s.to_date = '9999-01-01' ) sem,
(SELECT s.salary, s.emp_no, dm.dept_no
FROM salaries s
INNER JOIN dept_manager dm
ON s.emp_no = dm.emp_no
AND s.to_date = '9999-01-01' ) sdm
WHERE sem.dept_no = sdm.dept_no AND sem.salary > sdm.salary