要找出 oracle 中的第 N 个最大 Sal,我使用以下查询
To find out the Nth max sal in oracle i'm using below query
SELECT DISTINCE sal
FROM emp a
WHERE (
SELECT COUNT(DISTINCE sal)
FROM emp b
WHERE a.sal<=b.sal)=&n;
但根据我的说法,如果表大小很大,则使用上述查询将需要更多时间来执行.
But According to me by using the above query it will take more time to execute if table size is big.
我正在尝试使用以下查询
i'm trying to use the below query
SELECT sal
FROM (
SELECT DISTINCE sal
FROM emp
ORDER BY sal DESC )
WHERE rownum=3;
但没有得到输出......请提出任何建议......请分享有关如何优化查询和减少查询执行时间的任何链接.
but not getting output.. any suggetions please .. Please share any link on how to optimise queries and decrease the time for a query to execute.
试试这个
select *
from
(
select
sal
,dense_rank() over (order by sal desc) ranking
from table
)
where ranking = 4 -- Replace 4 with any value of N
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