题解 | #统计各个部门的工资记录数#

select t.dept_no, t.dept_name, count(1) as cnt
from
(select s.emp_no,s.salary,d.dept_no,dd.dept_name
from salaries s
left join 
dept_emp d
on s.emp_no =  d.emp_no
left JOIN
departments dd
on dd.dept_no = d.dept_no) t
group by t.dept_no, t.dept_name
order by t.dept_no asc

关联三张表，按照部门分组，统计条目数