How to change an existing column to auto-increment column in SQL Server?
In SQL server when you want to make an existing column to be auto-incremented.
The following code is not working:
ALTER TABLE [dwh].[ExchangeRate] ALTER COLUMN [ExchangeRateId] Int Identity(1, 1)
What you could do is :
- Create a new column with auto-increment
- Delete existing column constraint
- Delete the existing column
- Rename the new column back
- Add deleted constraint
Step 1: Create a new column
ALTER TABLE [dwh].[ExchangeRate] ADD [ExchangeRateId2] Int Identity(1, 1)
Step 2: Delete existing constraint
ALTER TABLE [dwh].[ExchangeRate] DROP CONSTRAINT [IxExchangeRate_ExchangeRateId_U_NC_]
Step 3: Delete existing column
ALTER TABLE [dwh].[ExchangeRate] DROP COLUMN [ExchangeRateId]
Step 4: Rename new column
Exec sp_rename 'dwh.ExchangeRate.ExchangeRateId2', 'ExchangeRateId','COLUMN'
Step 5: Add deleted contraint
ALTER TABLE [dwh].[ExchangeRate] ADD CONSTRAINT [IxExchangeRate_ExchangeRateId_U_NC_] PRIMARY KEY CLUSTERED ( [ExchangeRateId] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]