How to Alter Identity Column in SQL Server 2012
In SQL Server 2012, altering an identity column can be a crucial task when you need to modify the properties of a column that automatically generates unique values for each row. This article will guide you through the process of altering an identity column in SQL Server 2012, including the steps to change the seed, increment, and maximum value of the identity column.
Understanding Identity Columns
Before diving into the alteration process, it is essential to understand what an identity column is. An identity column is a type of column in a database table that automatically generates a unique value for each row inserted into the table. This unique value is often used as a primary key or a unique identifier for the rows. In SQL Server, identity columns are defined using the IDENTITY data type.
Steps to Alter Identity Column in SQL Server 2012
To alter an identity column in SQL Server 2012, follow these steps:
1. Open SQL Server Management Studio (SSMS): Launch SQL Server Management Studio and connect to your SQL Server instance.
2. Navigate to the Database and Table: In the Object Explorer, expand the server, then the database where the table with the identity column resides, and finally, expand the Tables folder.
3. Right-click on the Table: Right-click on the table that contains the identity column you want to alter and select “Design” from the context menu.
4. Modify the Identity Column: In the table design view, click on the identity column you want to alter. You will see three properties: Seed, Increment, and Maximum Value.
– Seed: The seed value is the starting value for the identity column. By default, it is set to 1. You can change it to any integer value.
– Increment: The increment value is the value by which the identity column is incremented with each new row. By default, it is set to 1. You can change it to any integer value.
– Maximum Value: The maximum value is the maximum value that the identity column can hold. By default, it is set to 2147483647 (2^31 – 1). You can change it to any integer value that is greater than the current maximum value.
5. Save the Changes: After making the desired changes, save the table design by clicking “Save” in the toolbar or pressing Ctrl + S.
6. Rebuild the Identity Column: To apply the changes to the existing data, you need to rebuild the identity column. To do this, execute the following SQL command:
“`sql
ALTER TABLE [YourTableName]
DROP COLUMN [YourIdentityColumnName];
ALTER TABLE [YourTableName]
ADD [YourIdentityColumnName] INT IDENTITY(1,1);
“`
Replace `[YourTableName]` with the name of your table and `[YourIdentityColumnName]` with the name of your identity column.
Conclusion
Altering an identity column in SQL Server 2012 is a straightforward process, provided you understand the properties and implications of the changes. By following the steps outlined in this article, you can easily modify the seed, increment, and maximum value of an identity column to suit your requirements. Remember to rebuild the identity column after making changes to ensure the new values are applied correctly.
