获取所有部门中当前员工薪水最高的相关信息,给出dept_no, emp_no以及其对应的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 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
));
max()函数返回数据中最大的一条,其与的忽略
select a.dept_no , a.emp_no , max(b.salary) as salary
from dept_emp as a join salaries as b
on a.emp_no = b.emp_no
where a.to_date = '9999-01-01' and b.to_date = '9999-01-01'
group by a.dept_no;