Jim Dettman
jimdettman at verizon.net
Thu Mar 3 12:40:33 CST 2011
Lambert, <<No you cannot just go in and change it at will. You also have to go find all the records in all the tables that use that Autonumber value as the foreign key back to the table they are relate to.>> Sorry if that wasn't obvious, but yes certainly you would. However I could do that at any time. Once it's turned into an attribute though, it takes on meaning. You still could at that point change it, but not without changing something else. It's no longer a matter of simply updating the data. For example, an asset tag number, which has been applied to all assets. New admin comes in and now wants all the numbers to be 4 digits instead of the current 8. I can't simply go into the data and decrease the digits without going to every asset and re-labeling it. Jim. -----Original Message----- From: accessd-bounces at databaseadvisors.com [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Heenan, Lambert Sent: Thursday, March 03, 2011 11:59 AM To: Access Developers discussion and problem solving Subject: Re: [AccessD] Access and SQL Server " However it can be made into a surrogate PK by assigning it to the object it's associated with, or in other words, making it an attribute. "Surrogate" means "to take the place of" and an auto number when it's just applied to a table cannot do that because it has no meaning. It's a pointer or tag in a physical context and that's it. Yes it is unique, but I can go in and change it at will." No you cannot just go in and change it at will. You also have to go find all the records in all the tables that use that Autonumber value as the foreign key back to the table they are relate to. So that's why I don't make an Autonumber PK any kind of meaningful attribute for a record. Real data used to construct Natural PKs can change too, and then it gets messy. Lambert's 2 cents. -- AccessD mailing list AccessD at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/accessd Website: http://www.databaseadvisors.com