SQL change table field self-increment identity

--Delete primary KEY constraint
DECLARE @Constraint_Name varchar (200)
Select @Constraint_Name = Name from dbo.sysobjects

where Xtype = ' PK ' and parent_obj =

(select [ID] from dbo.sysobjects

WHERE id = object_id (N ' [table name] ')

and OBJECTPROPERTY (ID, N ' isusertable ') = 1)
If @Constraint_Name <> '
Begin
ALTER TABLE name drop constraint @Constraint_Name
End
--Delete primary key field
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DECLARE @count int

Select @count = count (*) from sysobjects a,syscolumns b

where a.id = b.id and b.name = ' primary key field name ' and a.name = ' table name '
If @count > 0
Begin
ALTER TABLE table name drop column primary key field name
End

--Create fields, primary keys, and self-increment
ALTER TABLE name Add primary key field name int identity (PRIMARY key)

SQL change table field self-increment identity