题解 | 统计各个部门平均薪资
select department,round(avg(normal_salary-dock_salary),3) avg_salary from staff_tb i left join salary_tb s on i.staff_id=s.staff_id where s.normal_salary-s.dock_salary >=4000 and s.normal_salary-s.dock_salary<=30000 group by department order by avg_salary desc
!:where和having的区别