Query Performance

Hi,

I encountered a strange problem when i was trying to enhance a query! I've a query which selects simply all the records that were selected with in a subquery.
When i run the subquery alone it completes in a few seconds but when i include a select clause above it to choose the records retrieved by the sub query then it takes around six minutes. while i don't use any functions or manipulations in the outer select clause and neither i have any where clause associated.
Can some one tell me why this happens and help me with a work around for this?
Thanks in advance for your help.

Cheers,
Jaipaul.

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