How do I add auto_increment to a column in SQL Server 2008

Question

I am using SQL Server 2008 and a primary key of a database table I am using is not an IDENTITY column (not sure why). I need to change that.

I am in SQ

Answer 1

CREATE TABLE [dbo].[AR_Transactions](
       [Trans_ID] [bigint] IDENTITY(1,1) NOT NULL,
       [DateTime] [datetime] NOT NULL,
       [Cashier_ID] [nvarchar](50) NULL,
       [CustNum] [nvarchar](12) NOT NULL,
       [Trans_Type] [nvarchar](2) NOT NULL,
       [Prev_Cust_Balance] [money] NULL,
       [Prev_Inv_Balance] [money] NULL,
       [Trans_Amount] [money] NOT NULL,
       [Payment_Method] [nvarchar](4) NULL,
       [Payment_Info] [nvarchar](20) NULL,
       [Description] [nvarchar](38) NULL,
       [Invoice_Number] [bigint] NOT NULL,
       [Store_ID] [nvarchar](10) NOT NULL,
       [Dirty] [bit] NOT NULL,
       [Station_ID] [nvarchar](5) NULL,
       [Payment_Type] [smallint] NULL,

CONSTRAINT [pkAR_Transactions] 
       PRIMARY KEY CLUSTERED([Store_ID] ASC, [Trans_ID] ASC)
           WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, 
                 ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

ALTER TABLE [dbo].[AR_Transactions] 
    ADD CONSTRAINT [DF_AR_Transactions_Trans_ID_AR_Transactions] 
    DEFAULT ((0)) FOR [Trans_ID]

ALTER TABLE [dbo].[AR_Transactions] 
    ADD CONSTRAINT [DF_AR_Transactions_Invoice_Number_AR_Transactions] 
    DEFAULT ((0)) FOR [Invoice_Number]

Answer 2

You need to expand the "Identity Specification" node to change it via the (Is Identity) property.

This will rebuild the table so you might also need to go into Tools -> Options -> Designers -> Prevent saving changes that require table re-creation.

This can be an extremely time consuming operation on large tables as well as entailing a lot of logging and locking. To perform this operation on a large table see my answer here.

Answer 3

Remove the default constraint of column Trans_ID first. Then you can set Is Identity to Yes in the designer.

This is properties for column Trans_ID in your table AR_Transactions. (Is Identity) is disabled:

Remove the default constraint and (Is Identity) is no longer disabled:

Set to yes and save. Default Value or Binding is disabled instead:

Answer 4

To illustrate Martin's point:

And PS: - as Mikael Eriksson rightfully mentions (and documents nicely), this Identity Specification remains grayed out as long as that column you're working on has a default constraint.

Answer 5

You can't use ALTER TABLE ... ALTER COLUMN to modify a column to have an identity property. You'll need to

• drop the primary key constraint and any foreign key constraints referencing the column in question in your table.
• add a new column with the identity property. It should have the same type (int, I presume) as the existing column.
• update the table to seed the new column with the values of the existing column.
• alter the new column to make it non-nullable.
• drop the old/existing column.
• rename the new column so that its name is the same as that of the old column.
• Recreate the primary key and foreign key references you dropped in the 1st step.

Simple! Or something.