(that if a positive number is passed to the @Diff parameter):

yes it's possitive ,as you said there are many tables in my SP.

I'll have new DB every day,like this:

ISALOG_20110801_WEB_000.mdb

ISALOG_20110802_WEB_000.mdb

..

..

..

ISALOG_20110830_WEB_000.mdb

imagine that User wants to select 3 days.

I used Diff to find out which databases should be retrieve.if you look at databases name they have similar name :

ISALO_

_WEB_000.mdb

but dates are diffrent

20110801

20110802

....

20110830

so user select 3 days ,for instance 2011/08/01 to 2011/08/08

diff=2011/08/08 - 2011/08/01 (equal 8)

-----

In your OP, you said this SP returns 32,000 rows? 

well it would be more than 320,000 rows ,each table will have 320,000 or more.

imagine that 8 tables will have Avg=320,000*8

------

What does your application do with them?

in my Co ,they have TMG which stores users infortaion,something like they visited sites,logtime,Url,clientIp,browser and so on.

i want to report my users every day to find out which site they have visited,which browser they have used and so many availabe reports.

----

and thank you so much about responding me.