题解 | #统计各个部门的工资记录数#

先将部门员工关系表和薪水表联合，查出员工，薪水和部门的表

select s.emp_no,s.salary,d.dept_no from salaries s
left join dept_emp d
on s.emp_no=d.emp_no

之后进行联合，查出即可

select d.dept_no,d.dept_name,count(a.salary) as sum from departments d
join
(
select s.emp_no,s.salary,d.dept_no from salaries s
left join dept_emp d
on s.emp_no=d.emp_no
) as a
on d.dept_no=a.dept_no
group by d.dept_name
order by d.dept_no

不要忘了要按dept_no升序排列