>Vladimir's suggestion assumed that you have a PK in the child table (not that in proper design you didn't have one).

Yes, and you should always have one. When I was translating that code into Mike's structure I made a typo using wrong key.

BTW, Vladimir Maximov put this nicely into FAQ, but he told me that the idea originates from Igor Korolev.
So, they both deserve a credit.

BTW, I just used it recently myself the first time

* Idea by Igor Korolev 
SELECT * from curInvoice1 cI ;
WHERE cI.KyInvoice IN ;
(SELECT CTOBIN(RIGHT(MAX(PADL(Inv_amount,20,'0')+BINTOC(KyInvoice)),4)) ;  
  			FROM curInvoice1 GROUP BY CheckNum) ;
ORDER BY cI.CheckNum  INTO CURSOR curInvoice

I needed to pick up one invoice with the maximum amount in case we have several invoices.