1、将员工表和薪水表内连接,查询各部门工资记录数
select a.dept_no,count(b.salary) as `sum` from dept_emp a join salaries b on a.emp_no=b.emp_no group by a.dept_no2、将部门表和1表内连接,查询部门id,部门名称和工资记录数
select d.dept_no,d.dept_name,c.sum from departments d join (select a.dept_no,count(b.salary) as `sum` from dept_emp a join salaries b on a.emp_no=b.emp_no group by a.dept_no) as c on c.dept_no=d.dept_no order by d.dept_no;