Question

In SQL Server or maybe other databases, if a column is auto increment int type, the table can remember the highest value even if the record has been deleted.Let’s say you have a table whose with some records previously deleted, and then you use SELECT MAX([ColumnName]), it might return a value associated with a deleted record. Has anyone seen scenarios like this?

Answer 1

This will not happen with SELECT MAX (as can be seen from the below script) in Sql Server.

CREATE TABLE TEST_TABLE (
        ID INT IDENTITY (1,1),
        Val INT
)

INSERT INTO TEST_TABLE (Val) SELECT 1
INSERT INTO TEST_TABLE (Val) SELECT 2
INSERT INTO TEST_TABLE (Val) SELECT 3
INSERT INTO TEST_TABLE (Val) SELECT 4
INSERT INTO TEST_TABLE (Val) SELECT 5

DELETE FROM TEST_TABLE WHERE Val >= 3

SELECT  MAX(ID) MaxID
FROM    TEST_TABLE

DROP TABLE TEST_TABLE

Output

MaxID
2

If you were looking for the Tables Identity Value, see @AdaTheDev answer.