Question

table = emp

SAL
------
8000
7000
6000
5000
10000
9000
4000
8000
7000

对于上表，编写SELECT语句以显示最大和第二大Sals。您的输出应如下所示： -

          first     second
         -------    --------
           10000     9000

我写了以下查询，但我得到了以下输出：

select sal from (select rownum first, sal from(select distinct sal from emp1       order by sal desc))where first <= 2;

输出：

 SAL
----- 
10000  
9000

Answer 1

然后从您自己的请求中选择最小值和最大值，分成两个不同的列。

with   i
as     ( select sal
           from ( select rownum first
                       , sal
                    from ( select distinct sal
                             from scott.emp
                            order by sal desc ) )
          where first <= 2 )
select min ( i.sal )
     , max ( i.sal )
  from i
 group by i.sal;

Answer 2

另一种方法是使用DENSE_RANK函数;另外，如果您避开MIN / MAX，您可以根据需要获得任意Nth值：

with q as (
  select sal, dr from (
    select distinct
           sal
          ,DENSE_RANK() OVER (ORDER BY sal DESC) dr
    from   emp
  ) where dr in (1,2,10)
)
select (select sal from q where dr = 1) first
      ,(select sal from q where dr = 2) second
      ,(select sal from q where dr = 10) tenth
from dual;

查询（q）应该具体化，因此它的多个查询不应导致额外的数据传递。

我怎样才能得到以下输出？

2 个答案: