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IN subquery, with multiple fields
Message
De
31/10/2016 22:58:04
Hilmar Zonneveld
Independent Consultant
Cochabamba, Bolivie
 
 
À
31/10/2016 10:22:38
Information générale
Forum:
Visual FoxPro
Catégorie:
Codage, syntaxe et commandes
Versions des environnements
Visual FoxPro:
VFP 9
Divers
Thread ID:
01642525
Message ID:
01642579
Vues:
73
>>Can the "IN" clause, and a subquery, be used with multiple fields? I believe the answer is "no", but I wanted to confirm this.
>>
>>Example with one field:
>>
>>select * from MainTable where KeyField in (select KeyField in LookupTable)
>>
>>
>>For two fields, I was thinking something along the lines of:
>>
>>select * from MainTable where (KeyField1, KeyField2) in (select KeyField1, KeyField2) in LookupTable
>>
>>
>>But if I remember correctly, that resulted in an error.
>>
>>Assuming the answer is "no", and with respect to workarounds, I know I can use the "JOIN" instead; but how would I use the JOIN to emulate a NOT IN? I am pretty sure I can achieve this, but I am not sure about a more or less elegant way of doing this.
>>
>>Regards,
>>
>>Hilmar.
>
>How about
>
>
>>select * from MainTable mt where exists (select * from LookupTable lt  where lt.keyfield1=mt.keyfield1 and lt.keyfield2 = mt.keyfield2 )
>>
Oh, OK, I guess I have never really used the "exists" option. I'll have to try it out. Thanks.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)
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