What happens when DB engine runs out of numbers to use for primary keys?

Question

Since DBs do not reuse numbers of deleted records it is possible to run out of numbers, especially if you pick not really a big integer type for this column.
What would

Answer 1

I tried this in SQL 2000 some time ago. After Integer.MaxValue the next identity value is Integer.MinValue. It then keeps counting up as you would expect. As long as the records that used to exist at 1,2,3 etc have gone by the time it gets there nothing bad will happen. If it runs into a duplicate (and the field is the primary key) then the insert fails with a key violation. I haven't tried an identity column that isn't constrained to unique values though. I would guess it would be happy with the duplicates.