>>>Hi Jim,
>>>
>>>>>When i execute the folowing SQL query, i get the error colomn "WTG"not found.
>>>>>
>>>>>SELECT detail.avr_ari,;
>>>>> iif(Detail.avr_wtg=.t.,'J','N') as WTG;
>>>>>FROM general!detail;
>>>>>WHERE WTG='J'
>>>>>
>>>>>Is this an impossible kind of query, to include an expressionalias in the WHERE Clause ?
>>>>>
>>>>>Any idea's how to solve this ?
>>>>>
>>>>
>>>>Bjorn,
>>>>
>>>>The WHERE clause of SELECT si applied to the source tables, there is no fild named WTG in the source fields. You can change it to;
>>>>
>>>>WHERE Detail.avr_wtg = "J"
>>>>
>>>
>>>This will cause a data-type mismatch. If he's testing against the result of the iif(), he's got to use the HAVING clause.
>>
>>Naw, you don't need a HAVING or a comparison operator, simply

SELECT detail.avr_ari, "J" AS WTG;
>>FROM general!detail;
>>WHERE Detail.avr_wtg

will do the trick. Using Detail.avr_wtg = .T. slows things down.
>
> George,
>
> If you have index on avg_wtg (though it would be strange to have index on logical field), I assume, where avr_wtg=.t. should be faster than where avr_wtg
>
>Correct me, please, if I'm wrong.

No, it wouldn't be. This is because whenever you have a comparison operator, both sides of the expression must be evaluated.