题解 | #统计各个部门的工资记录数#
统计各个部门的工资记录数
https://www.nowcoder.com/practice/6a62b6c0a7324350a6d9959fa7c21db3
select
t1.dept_no,
t1.dept_name,
count(*) as sum
from
(select dept_no, dept_name
from departments) as t1
left join
(select emp_no, dept_no
from dept_emp)as t2
on t1.dept_no = t2.dept_no
left join
(select salary, emp_no
from salaries) as t3
on t3.emp_no = t2.emp_no
group by t1.dept_no,t1.dept_name
主打一个使劲连