Adding Identity to an Existing SQL Server Column: Two Methods
Directly adding an identity property to an existing column in SQL Server isn't a simple task. This article outlines two methods to achieve this, each with its own trade-offs:
Method 1: Creating a New Table with Identity
This method preserves existing data.
CREATE TABLE dbo.Tmp_Names ( Id INT NOT NULL IDENTITY(1, 1), Name VARCHAR(50) NULL ) ON [PRIMARY] GO SET IDENTITY_INSERT dbo.Tmp_Names ON GO IF EXISTS (SELECT * FROM dbo.Names) INSERT INTO dbo.Tmp_Names (Id, Name) SELECT Id, Name FROM dbo.Names TABLOCKX GO SET IDENTITY_INSERT dbo.Tmp_Names OFF GO DROP TABLE dbo.Names GO EXEC sp_rename 'Tmp_Names', 'Names'
Method 2: Adding a New Identity Column and Replacing the Old
This approach does not retain existing data in the new identity column.
ALTER TABLE Names ADD Id_new INT IDENTITY(1, 1) GO ALTER TABLE Names DROP COLUMN ID GO EXEC sp_rename 'Names.Id_new', 'ID', 'COLUMN'
Important Considerations:
Remember to address any foreign key constraints linked to the original primary key column before implementing either method. Failure to do so will result in database errors.
For more detailed information and troubleshooting, consult this Microsoft SQL Server forum thread:
https://www.php.cn/link/16dd8c942ad630be7e5a12b681b3f5c4
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