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How to join 3 tables
Message
De
21/10/2003 19:17:38
 
 
À
21/10/2003 19:00:26
Hilmar Zonneveld
Independent Consultant
Cochabamba, Bolivie
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Divers
Thread ID:
00840872
Message ID:
00840892
Vues:
23
>>>If you need to join the SECOND table to the third, the syntax becomes a little more involved; you have to insert stuff between the JOIN and ON, thusly:
>>>
>>>
>>>sele a.pn ;
>>>   from pnvendor a;
>>>      left join inv b;
>>>         left join Table3 on b.KeyField = Table3.KeyField;
>>>      on a.pn = b.pn ;
>>>   where [SomeCondition]
>>>
>>>
>>>Note that I alligned the first LEFT and the last ON, to indicate they go together.
>>>
>>
>>Actually, you don't have to.
>
>Yes, I know. Allignment is irrelevant for VFP. It helps the programmer keep things clear - and the reason I pointed this out is to indicate which commands go together. Understanding this can be important for more complicated queries.

I mean you don't have to nest them. This works the same, and is easier to read.
sele a.pn ;
   from pnvendor a;
      left join inv b on a.pn = b.pn ;
      left join Table3 on b.KeyField = Table3.KeyField ;
   where [SomeCondition]
Insanity: Doing the same thing over and over and expecting different results.
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