题目描述
查找各个部门当前(dept_manager.to_date=‘9999-01-01’)领导当前(salaries.to_date=‘9999-01-01’)薪水详情以及其对应部门编号dept_no
注:输出结果以salaries.emp_no升序排序,并且请注意输出结果里面dept_no列是最后一列
CREATE TABLE `salaries` (
`emp_no` int(11) NOT NULL, -- '员工编号',
`salary` int(11) NOT NULL,
`from_date` date NOT NULL,
`to_date` date NOT NULL,
PRIMARY KEY (`emp_no`,`from_date`));
CREATE TABLE `dept_manager` (
`dept_no` char(4) NOT NULL, -- '部门编号'
`emp_no` int(11) NOT NULL, -- '员工编号'
`to_date` date NOT NULL,
PRIMARY KEY (`emp_no`,`dept_no`));
实现
select salaries.*,dept_manager.dept_no
from salaries
left join dept_manager on salaries.emp_no = dept_manager.emp_no
where dept_manager.to_date='9999-01-01' and salaries.to_date='9999-01-01'
order by salaries.emp_no
关于left join 左连接/右连接,可参考
https://blog.csdn.net/weixin_39220472/article/details/81193617