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
三表连接， 然后用group by
select d.dept_no, d.dept_name, count(s.salary) as sum
from departments d join dept_emp e
on d.dept_no=e.dept_no
join salaries s
on e.emp_no = s.emp_no
group by d.dept_no
order by d.dept_no asc;
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