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JOIN vs WHERE
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À
17/06/2009 14:24:22
Information générale
Forum:
Visual FoxPro
Catégorie:
Codage, syntaxe et commandes
Titre:
Versions des environnements
Visual FoxPro:
VFP 8 SP1
Divers
Thread ID:
01406428
Message ID:
01406704
Vues:
40
>>>Please Note: VFP 8
>>>
>>
>>PS: Both queries should return wrong count but I don't know what you really want to count (couldn't visualize).
>>
>>Maybe this one:
>>
SELECT  cust.customer, COUNT(fr.custshipm) ;
>>   FROM crsAllCust cust;
>>      LEFT JOIN crsFillRate fr ON cust.customer = fr.custshipm AND EMPTY(fr.PartOrders);
>>   GROUP BY cust.customer
>>
>>Cetin
>
>The original query actually had COUNT(fr.custshipm). I tested with COUNT(*) and got the same results. And that was the code I cut and pasted. I also tried it with COUNT(*) and COUNT(fr.custshipm) and both fields had the same values.

Count(*) inlcudes NULL values into the result and Count(Field) excludes the NULL values. This is the main difference.

So, Count(*) should have included records with no match and count(RightTable.Field) should have only counted records that match.
If it's not broken, fix it until it is.


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