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LEFT JOIN vs FULL JOIN
Message
De
17/06/2011 11:09:16
Hilmar Zonneveld
Independent Consultant
Cochabamba, Bolivie
 
 
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Versions des environnements
Visual FoxPro:
VFP 9 SP1
Divers
Thread ID:
01514564
Message ID:
01514897
Vues:
37
>Thank you for the example. I, like you, have never, until this particular case, used FULL JOIN. I was always concerned about Cartesian join. But in this case, because the FROM table has a unique entry FULL JOIN seem to work well.

A Cartesian product is done in Visual FoxPro by omitting a condition:
select Table1.Field1, Table2.Field2;
  from Table1, Table2
In Oracle I learned to use the explicit clause CROSS JOIN for the same purpose; I believe this is ANSI standard, but not supported in Visual FoxPro.

Full outer join is different - it is simply a combination of LEFT and RIGHT - non-matching records on both sides are included. I don't quite understand your example, but I strongly suspect that a LEFT or RIGHT join would be sufficient. As I mentioned, I haven't seen a practical application for a FULL OUTER join.
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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