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What to use instead of _tally for SUM() SQL Select?
Message
De
29/11/2005 09:13:23
 
 
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Versions des environnements
Visual FoxPro:
VFP 9
Divers
Thread ID:
01072776
Message ID:
01072792
Vues:
13
>>>>>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.
>
>Thank you for confirming the "correct" approach.

This .null. value actually was introduced in VFP9, in earlier versions you had to use the count(1) solution.
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