取得薪水最高的第六到第十名员工

select * from emp order by sal desc limit 5,5

取得最后入职的5名员工

select * from emp order by hireDate desc limit 5

取得每个薪水等级有多少员工

第1步：查询每个员工的工资等级

select empNo,sal,grade from emp,salgrade where sal between loSal and hiSal

第2步：将“第1步”查询结果看成临时表t，分组统计t.grade的个数。

select t.grade,count(t.empNo) as count from (select empNo,sal,grade from emp,salgrade where sal between loSal and hiSal) t group by t.grade