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?

Thanks