>Hi George,
>>>>>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 ?
>>>>>

You can't reference the results of the SELECT during the WHERE, because the resulting element doesn't exist. You have two basic choices:

WHERE detail.avr_wgt

oe defer the decision until the result set is formed, and place it in the HAVING clause:

HAVING WTG = 'J'

>>>>>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.
>
>I agree you don't HAVE to use HAVING to solve this problem. BUT, if you need to test against the result of the iif() (or any function for that matter) you need to use the HAVING clause. That was my intended point.
>
>BTW, Is it REALLY faster to skip the '= .T.'? I've never tested that. I tend to be explicit so that my SQL converter can parse more easily for SPT to SQL Server or (soon) Oracle.