SQL Server 2008+
I have a table with an auto-increment column which I would like to have increment not only on insert but also update. This column is not the primary key, but there is also a primary key which is a GUID created automatically via newid().
As far as I can tell, there are two ways to do this.
1.) Delete the existing row and insert a new row with indentical values (plus any updates).
or
2.) Update the existing row and use the following to get the “next” identity value:
IDENT_CURRENT('myTable') + IDENT_INCR('myTable')
In either case, I’m forced to allow identity inserts. (With option 1, because the primary key for the table needs to remain the same, and with option 2 because I’m updating the auto-increment column with a specific value.) I’m not sure what the locking/performance consequences of this are.
Any thoughts on this? Is there a better approach? The goal here is to maintain an always increasing set of integer values in the column whenever a row is inserted or updated.
I think a column of type rowversion (formerly known as “timestamp”) might be your simplest choice, although at 8 bytes these can amount to fairly large integers. The “timestamp” syntax is deprecated in favor of rowversion (since ISO SQL has a timestamp datatype).
If you stay with the Identity column approach, you would probably want to put your logic into an UPDATE trigger, which would effectively replace the UPDATE with the INSERT and DELETE combination you’ve described.
Note that Identity column values are not guaranteed to be sequential, only increasing.