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
http://www.nowcoder.com/practice/6a62b6c0a7324350a6d9959fa7c21db3
以salaries为主表，两表联查
select dept_no,dept_name,count(*) sum
from salaries left join dept_emp using(emp_no)
left join departments using(dept_no)
group by dept_no
order by dept_no
