> I'm using Oracle 9i. I need an equivalent of Sql Server's SELECT TOP
> with ORDER BY.
> I have found two different approaches to do this.
> 1- Declaring a cursor and fetching the rows I need.
> 2- Using a nested query to order the table in the inner select and
> rownum in the outer.
>
> Both solutions work right, but I want to know which has a better
> performance when my tables become large, i.e. more than 10K records.
> I guess that if I create an index on the column I order by there
> should be no significant differences in performance between those
> solutions, but I'm not sure.
>
> Can anybody give some advice?
You don't need a nested query:
SELECT a FROM t ORDER BY b WHERE rownum < 10
will work just fine, and probably have the best performance.
An index on b could be used to eliminate the sort, but I don't think
it will make a big difference with just 10k rows
Received on Wed Jan 07 2004 - 16:09:18 CST
