Oracle HASH GROUP BY & SORT GROUP BY performance

[Ratan Kumar]

Hi,

I have a select query which uses GROUP BY and HAVING clause performing selct over 3 million records.

In oracle 10g one version (i think rel 2), the explain plan shows HASH GROUP BY and this query runs very fast.

In oracle 10g another version (i think rel 1), the explain plan shows SORT GROUP BY and this query takes hours.

Pls suggest what should i do? Is there any hint that can make the query use HASH GROUP BY instead of SORT GROUP BY.
Or is there any other option that i should try?

Thanks in advance.