Group by 总结 时光慢点走~~
Group by 的使用
需求 查询每个部门最高的薪资
select bumen , max(salary) maxsal from dept group by bumen ;
select bumen , max(salary) maxsal from dept group by bumen ;
需求 查询每个部门薪资的总和
select bumen ,sum(salary) sumsal from dept group by bumen ;
需求 查询公司2013年入职的各个部门每个级别里的最高薪
select name,bumen, max(salary) from dept where hirdate =2013 group by bumen ;
需求 寻找雇员数超过2个的部门的最高和最低薪水
select name ,bumen,max(salary) ,min(salary) from dept group by bumen having count(bumen)>=2;
需求 寻找雇员平均工资大于3000的部门的最高和最低薪水
select bumen ,max(salary),min(salary) from dept group by bumen having AVG(salary)>3000