从当前值重新设置SQL自动增量

Question

I am trying to reseed the auto increment value from the current auto increment value of the table in SQL. I did something like

USE [MyDatabase]
GO

SELECT IDENT_CURRENT('MyTable') AS Current_Identity
DBCC CHECKIDENT (MyTable, reseed, Current_Identity)

I get the following error:

(1 row(s) affected)
Msg 2560, Level 16, State 9, Line 3
Parameter 3 is incorrect for this DBCC statement.

Any idea whats going wrong?

Answer 1

In SQL Server, you could save the IDENT_CURRENT value in a variable, like this:

DECLARE @currentIdentity INT;
SELECT @currentIdentity = IDENT_CURRENT('MyTable');
DBCC CHECKIDENT (MyTable, reseed, @currentIdentity);

To answer your question, your problem is that Current_Identity is an alias to a column, but you did not store it anywhere. This means that the next call you make to DBCC CHECKIDENT cannot reference the column from the previous query.

Answer 2

If you run the following code on a table that never had a record in it, you will the following error :

Parameter 3 is incorrect for this DBCC statement

DECLARE @max_id INT
SELECT @max_id = MAX(ID)+1 FROM testt; 
DBCC CHECKIDENT('Tablename',RESEED,@max_id);

The reason is that @max_id is NULL in this case and you can't pass it.

Here is what I would do. I would check the value returned to make sure it's not NULL. Hope this helps

DECLARE @max_id INT, @var int
SELECT @max_id = MAX(ID)+1 FROM TABLENAME; 
IF @max_id IS NULL 
BEGIN
SELECT@var = 1 
END
ELSE
BEGIN 
SELECT @var = @max_id
END
DBCC CHECKIDENT('TABLENAME,RESEED,@var);