Reset Identity column in SQL Server

Question

I am making an SQL database that stores contacts. I want to be able to delete contacts, and the correct id for each contact is crucial for my software connecting to it. Lets

Answer 1

A 1 minute google search gave me a page that I can't display. Google this and it'll be your first link as of 6/1/2009: tsql fix "identity column"

Essentially, I would suggest adding a foreign key constraint between all of your relational fields to the ID field in question prior to doing any renumbering (which is also a horrible idea if there are any relationships whatsoever, strictly because if you are asking this question, you will have a heck of a time).

If your contacts table is your ONLY table or has ZERO relationships based on this ID field, you could set the Identity property to NO, renumber the values from 1 to COUNT(ID), then set the Identity property to YES, and reseed the identity for completion using:

DECLARE @MaxID INT

SELECT @MaxID = COUNT(ID) FROM TableID

DBCC CHECKIDENT('TableID', RESEED, @MaxID)

In this scenario, you could use the above reseed script after each set of deletions (but change COUNT(ID) to MAX(ID) once everything is initially and correctly set up, this adds a little speed as the table gets larger), prior to any additional inserts or foreign key constraint updates. Ensure you use TRANSACTIONS wrapped around the deletes and reseeding blocks, and ensure the table only allows synchronous transactions, this will prevent any data hosing in the middle of the reseeds.

Complex eh? That's why it's best to start out on the right foot. ;) (I learned this from experience) E-mail me at mraarone et yahoo d0t com if you have any more questions.