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LEFT JOIN vs FULL JOIN
Message
 
 
À
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:
01514902
Vues:
40
>>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.

First, thank you for clarifying what Cartesian product is. I understand it better now.

As far as me using the FULL JOIN I showed an example to Naomi and she agreed that FULL JOIN will work better for me. I can dig out that example and present it here again. But in description the reason I need FULL JOIN is that both the table on the LEFT and RIGHT of the join have unique/different records. And I am trying to create a query/cursor that will have unique records from both sides. This is why FULL JOIN works for me.
"The creative process is nothing but a series of crises." Isaac Bashevis Singer
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