Question

I have a table with column ID that is identity one. Next I create new non-identity column new_ID and update it with values from ID column + 1. Like this:

new_ID = ID + 1 

Next I drop ID column and rename new_ID to name ‘ID’.

And how to set Identity on this new column ‘ID’?

I would like to do this programmatically!

Answer 1

As far as I know, you have to create a temporary table with the ID field created as IDENTITY, then copy all the data from the original table. Finally, you drop the original table and rename the temporary one. This is an example with a table (named TestTable) that contains only one field, called ID (integer, non IDENTITY):

BEGIN TRANSACTION GO CREATE TABLE dbo.Tmp_TestTable     (     ID int NOT NULL IDENTITY (1, 1)     )  ON [PRIMARY] GO SET IDENTITY_INSERT dbo.Tmp_TestTable ON GO IF EXISTS(SELECT * FROM dbo.TestTable)      EXEC('INSERT INTO dbo.Tmp_TestTable (ID)         SELECT ID FROM dbo.TestTable WITH (HOLDLOCK TABLOCKX)') GO SET IDENTITY_INSERT dbo.Tmp_TestTable OFF GO DROP TABLE dbo.TestTable GO EXECUTE sp_rename N'dbo.Tmp_TestTable', N'TestTable', 'OBJECT'  GO COMMIT