Thanks Sergey!

>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?
>>