题解 | #获取每个部门中当前员工薪水最高的相关信息#
统计各个部门的工资记录数
http://www.nowcoder.com/practice/6a62b6c0a7324350a6d9959fa7c21db3
莫忘deptno排序: select d.dept_no, de.dept_name, count(*) sum from dept_emp d left join departments de on d.dept_no = de.dept_no left join salaries s on d.emp_no = s.emp_no group by d.dept_no,de.dept_name order by d.dept_no