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Left join proper syntax
Message
De
31/10/2000 15:53:01
Jonathan Cochran
Alion Science and Technology
Maryland, États-Unis
 
 
À
31/10/2000 13:34:09
Information générale
Forum:
Visual FoxPro
Catégorie:
Codage, syntaxe et commandes
Divers
Thread ID:
00436236
Message ID:
00436514
Vues:
23
The problem that I was experiencing was related to filtering on an indexed child field (in either the Join or Where clause). If the expression could be optimized, I would get all parent records, regardless of whether they matched the child filter or not. This only happened when my child filter was on Child.ChildField = " " or Child.ChildField = 0. When the filter can be optimized, it basically treats each parent record as having a "phantom" child record pulled in by the Left Outer join, and the child fields for these "phantom" records have the FoxPro default values of blank, 0, etc. (depending on the data type), so they therefore match the filter.

>>I was told by some people (including support at Microsoft) that doing a Left Outer join and filtering on the child table is not a logical thing to do. However, no one provided another alternative to get the data that I wanted.
>
>What data were you trying to get? As Michel learned, when you filter the child after an outer join, the records added by the outer join fall out.
>
>Tamar
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