Oracle Database Discussions

Hello everybody.

I have performance problem.
I using Oracle 11g, Windows server 2003.

I have 3 tables:
1. my_documents -> About 850,000 records.
2. relat_documents_groups -> About 10 records.
3. relat_documents_projects -> About 850,000 records.


I'm executing this query:

select d.document_id from my_documents d
LEFT JOIN relat_documents_groups rdg
ON d.version_label = rdg.version_label
INNER JOIN relat_documents_projects rdp
ON d.document_id = rdp.document_id
order by document_id desc

It's takes 4 seconds until the data retrives.
But if i remove the "Order by" clause (last row) it's takes 0.3 seconds.

Why 'Order By' takes more than 3 seconds? How can i improve this?

I don't think i need to improve my query because the same query runs on MSSQL 2005 in less

than 1 second (on the same tables and rows).
I think it's something with the DataBase itself but i don't know what.

Is anybody know?

Thanks,
MTs.