>Hi Sergey,
>
>Sorry for the delay, thanks for the right and brief reply, I have another question, why is that if we use condition in SQL, like you wrote t1.fieldnm = t2.fieldnm , it doesn't give rushmore optimization, but that doesn't happend if use condition like t1.fieldnm = 'varname' .
>

It depends. Either of them could be optimzable or not. See 'Using Rushmore to Speed Data Access' in the help or at http://msdn.microsoft.com/library/default.asp?url=/library/en-us/fox7help/html/dgusing_rushmore_to_speed_data_access.asp.