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]