【作业】2022.5.25 MySQL 查操作2

-- 查询月薪最高的员工姓名和月薪
select  ename as 员工姓名, 
        max(sal) as 最高月薪
  from  tb_emp;

-- 查询员工的姓名和年薪(年薪=(sal+comm)*13)
select ename as 员工姓名,
	   (sal + ifnull(comm, 0)) * 13
from tb_emp;

-- 查询有员工的部门的编号和人数
   select  dno as 部门编号,
		   count(*) as 人数
     from  tb_emp natural join tb_dept
 group by  dno;

-- 查询所有部门的名称和人数
   select  tb_dept.dno as 部门编号,
		   count(eno) as 人数
     from  tb_emp right join tb_dept
       on  tb_emp.dno = tb_dept.dno
 group by  tb_dept.dno;

-- 查询月薪超过平均月薪的员工的姓名和月薪
  select  ename as 员工姓名,
	      sal as 月薪
    from  tb_emp
   where  sal >= (select  avg(sal) as 平均月薪 from tb_emp)
order by  sal;

-- 查询月薪超过其所在部门平均月薪的员工的姓名、部门编号和月薪
   select  ename as 员工姓名,
		   dno as 部门编号,
           sal as 月薪
     from  tb_emp t1 natural join (  select  dno,
									         avg(sal) as 平均月薪
								       from  tb_emp
                                   group by  dno) t2
    where  sal >= 平均月薪
 order by  dno, sal;

-- 查询部门中月薪最高的人姓名、月薪和所在部门名称
  select  ename,
          max(sal),
          dname
    from  tb_emp natural join tb_dept
group by  tb_dept.dno;

-- 查询主管的姓名和职位
select  ename,
        job
  from  tb_emp
 where  eno in (select  mgr 
                  from  tb_emp);

-- 查询月薪排名4~6名的员工排名、姓名和月薪
select  排名,
		ename as 姓名,
        sal as 月薪
  from  (select  rank() over (order by sal desc) as '排名',
                 ename,
                 sal
           from  tb_emp) t2
 where  排名 <= 6 
   and  排名 >= 4;

-- 查询每个部门月薪排前2名的员工姓名、月薪和部门编号
select  ename as 员工姓名,
        sal as 月薪,
	    dno as 部门编号
  from  (select  ename,
		         sal,
		         dno,
		         rank() over (partition by dno order by sal desc) as 'rank_num'
           from  tb_emp) t2
 where  rank_num <= 2;