As a variant on John's technique, I'll combine fields into a single text block that I then run through a fast hashing algorithm that returns a longint.
What good is that longint? It helps in two cases: * If you're comparing two copies of the same record during an update/sync, etc., then you can hash the new copy and see if the hash differs from the stored original. If they match, you can figure there's been no update. [Subject to availability, limitations apply. See 'hashing' for complete terms and details.] * When you don't know if the row is a duplicate or not, hash the incoming data and see if it matches something else. If it does not match, you've got a new row. If it does match one or more rows, you *might* have a duplicate, but at least you only need to gets a small # of records to find out. Regarding hashing, I don't use SHA1, MD5, etc. Because I don't need them and don't want the overhead. Instead I use some hashing functions from an old (10+ years ago) tech notes. They still work great and are a good match for exactly this sort of application. ********************************************************************** 4D Internet Users Group (4D iNUG) FAQ: http://lists.4d.com/faqnug.html Archive: http://lists.4d.com/archives.html Options: http://lists.4d.com/mailman/options/4d_tech Unsub: mailto:4d_tech-unsubscr...@lists.4d.com **********************************************************************
