>>>The variable _tally indicates if SQL Select found any records. However, if the SQL Select has SUM() function _tally returns value of 1, even though there were no records matching WHERE.
>>>
>>>What do you recommend to use, instead of _tally, to check if SQL Select found records?
>>>
>>>Thank you.
>>
>>Add one column, count(1) as nTally.
>
>I will think about this, although, this may slow the query (maybe not significantly though). I found a solution, I think. The resulting value of SUM() function has NULL if no records match the WHERE clause.
>
>Thank you.

Checking for .null. is the "correct" way, I did not read your message carefully. Anyway, adding "count(1) as ntally" will only make a marginal change to the select speed, if at all measurable.