Question

If you add a new record, then delete the record, then add it again over and over, in time, sooner or later, when you add a new record the integer primary key id, it will eventually exceed 2 billion.

1. Now what happens? SQL Server will start the primary key id from 1 again? or -1?

2. What happens if it cycles 4 billion times; how does SQL Server know not to replace the previous data?

Answer 1

You get an error if the identity would exceed the bounds of the datatype making the rest of your question moot. You can see this by

CREATE TABLE #T
(
id INT IDENTITY(2147483647,1)
)

INSERT INTO #T
DEFAULT VALUES

INSERT INTO #T
DEFAULT VALUES /*Arithmetic overflow error converting IDENTITY to data type int.*/

GO

SELECT * FROM #T

DROP TABLE #T