Upper limit for autoincrement primary key in SQL Server

Question

What is the upper limit for an autoincrement primary key in SQL Server? What happens when an SQL Server autoincrement primary key reaches its upper limit?

Answer 1

Joel's answer is correct, it is the upper limit of whatever datatype you use.

Here's an example of two of them:

• int: 2^31-1 (2,147,483,647)
• bigint: 2^63-1 (9,223,372,036,854,775,807)

I have actually hit the limit at a job I worked at. The actual error is:

    Msg 8115, Level 16, State 1, Line 1
    Arithmetic overflow error converting IDENTITY to data type int.
    Arithmetic overflow occurred.

There are a couple fixes to this I can think of off the top of my head. Number 1 is probably very hard and not very likely, number 2 is easy, but will probably cause problems in your code base.

1. If the identity column doesn't matter to you (it's not a Foreign Key, etc.) then you can just reseed the database and reset the identity column.
2. Change your identity column to a bigger number. So for example if you've overflowed an int, change your identity column to a big int. Good luck overflowing that :)

There are probably other fixes, but there is no magic bullet easy one. I just hope this doesn't happen in a table that is the center of a bunch of relationships, because if it does, you're in for a lot of pain. It's not a hard fix, just a tedious and long one.