So...are JOINS generally faster than using the subset version?
I was just going to ask if the following would be better implemented with JOINS.
SELECT * FROM crsMatchResults ;
INTO CURSOR crsMatchResults ;
WHERE ;
(Sequence in (SELECT Sequence FROM crsSurvivors) OR ;
Sequence in (SELECT Sequence FROM crsDuplicates)) AND ;
(GroupNum in (SELECT GroupNum FROM crsSurvivors) AND ;
GroupNum in (SELECT GroupNum FROM crsDuplicates)) ;
ORDER BY Sequence ;
READWRITE NOFILTER
Aloha,
James
>It's unknown how VFP handles such conditions but most likely it creates a cursor with subquery and then matches each record from the main table to it. The following command should be faster
UPDATE Invoices ;
> SET InvoiceId = "ABC123" ;
> FROM Invoices
> JOIN Invoices2 ON Invoices2.RecordId = Invoices.RecordId
>
>
>>I have the following command:
>>
>>
>>UPDATE Invoices;
>> SET InvoiceId = "ABC123";
>> WHERE RecordId IN;
>> (SELECT RecordId
>> FROM Invoices2)
>>
>>
>>
>>
>>
>>1) Does VFP first create a subset of Invoices2.RecordId and then use that
>>to drive the update Invoices? Or is each record in Invoices2 evaulated
>>for every record in Invoices?
>>
>>2) Is there a more efficient way to do this?
>>