Is there anyway to reset the identity of a Table Variable?

Question

Say I have a table variable:

DECLARE @MyTableVar TABLE (ID INT IDENTITY(1,1), SomeData NVARCHAR(300))

After I have inserted 250 rows, I nee

Answer 1

Can you use temporary table? This is a sample how to do this with a temp table.

CREATE TABLE #MyTableVar (ID INT IDENTITY(1,1), SomeData NVARCHAR(300))

insert #MyTableVar(SomeData) values ('test1'), ('test2')

---doesn't work
DELETE FROM #MyTableVar 

insert #MyTableVar(SomeData) values ('test3'), ('test4')
select * from #MyTableVar 

--resets the identity
truncate table #MyTableVar
insert #MyTableVar(SomeData) values ('test3'), ('test4')
select * from #MyTableVar 

Regards

Piotr

Answer 2

unfortunately there is no function to reseed identity column in table variable, I know this question is very old, but in case other people encountered the same problem, I would like to share my method to solve this problem.

/* declare another table variable with same structure and perform select insert*/

DECLARE @MyTableVar1 TABLE (ID INT IDENTITY(1,1), SomeData NVARCHAR(300))
insert into @MyTableVar1
select someData from @MyTableVar

However, If you want to perform dynamic reseeding inside a loop, I would suggest using a table object

Answer 3

Instead relying on an Identity, why not use the new ranking functions such as Row_Number

Insert @MyTableVar( Id, Value )
Select Row_Number() Over ( Order By Value )
    , Value
From SomeOtherTable

Answer 4

Instead of re-seeding the IDENTITY, why not just delete from the @table variable, then use ROW_NUMBER() against the input? e.g. instead of the lazy

SELECT * FROM @MyTableVar;

...use...

SELECT ID = ROW_NUMBER() OVER (ORDER BY ID), SomeData FROM @MyTableVar;

Now you don't need to care what the seed is, whether it starts at 1, whether there are any gaps, etc.

Answer 5

you should truncate your table instead of deleting all rows from it.

but note that truncate will not work for some tables, (listed from MSDN):

You cannot use TRUNCATE TABLE on tables that:

Are referenced by a FOREIGN KEY constraint. (You can truncate a table that has a foreign key that references itself.)

Participate in an indexed view.

Are published by using transactional replication or merge replication.

and added myself:

You cannot truncate a table variable.

syntac of truncate is:

TRUNCATE TABLE 
    [ { database_name .[ schema_name ] . | schema_name . } ]
    table_name
[ ; ]

EDIT: I didn't notice that you are questioning about table variables.

as far as I know there is no way to reset an identity column in a table variable. you can use a temp table instead.

Answer 6

I tried it on net but i am not able to get any solution on reset identity for table variable.

If you are able to use temp table #MyTableVar instead of table @MyTableVar variable then it is possible to reset identity value

   DBCC CHECKIDENT('TableName', RESEED, NewValue)

   DBCC CHECKIDENT(#MyTableVar, RESEED, 0)

Newvalue must be one less than the newIdentiyValue

   NewValue= NewIdentity-1;

If you still want to learn more you can refer my blog http://tryconcepts.blogspot.in/2012/08/reset-identity-column-to-new-id.html