**

----------------分组查询

**

（1）查询至少有一个员工的部门编号。
select DEPARTMENT_ID
from EMPLOYEES
group by DEPARTMENT_ID
having count(*)>0;

（2）查询各个部门中不同职位的最高工资。
select DEPARTMENT_ID ,JOB_ID,max(SALARY)
from EMPLOYEES
group by DEPARTMENT_ID,JOB_ID;

（3）查询各个部门的人数及平均工资。
select DEPARTMENT_ID ,count(*) ,avg(SALARY)
from EMPLOYEES
group by DEPARTMENT_ID;

（4）统计各个职位的员工人数与平均工资。
select JOB_ID , count(*) , avg(SALARY)
from EMPLOYEES
group by JOB_ID;

（5）统计每个部门中各职位的人数与平均工资。

select DEPARTMENT_ID ,JOB_ID,count(*),avg(SALARY)
from EMPLOYEES
group by DEPARTMENT_ID,JOB_ID;

(6) 查询最低工资大于5000元的各职位。

Select JOB_ID ,avg(SALARY)
from EMPLOYEES
Group by JOB_ID
having min(SALARY)>5000;