Order No field is available in all purchase related Tables
Order No Field is available in header and line . Order No for header will useful when you want to do purchase reciept , posted purchase invoice and want to know what is its Order no or source no
Order No at line level is useful when you pull mutilple reciepts for invocing . In a single invoice you can have multiple POs and multiple Receipts . At this instance line level data is helpful
Warm Regards
Pallavi Phade