How to Alter Table Identity Column in SQL Server 2008
Managing database tables in SQL Server 2008 often requires making changes to the structure of the tables. One common modification is altering the identity column of a table. The identity column is a special type of column that automatically generates unique values for new rows inserted into the table. This article will guide you through the process of altering the identity column in SQL Server 2008, including the steps to change the seed, increment, and maximum values of the identity column.
Before proceeding with the alterations, it is essential to understand the purpose of each parameter:
1. Seed: The starting value of the identity column. It defines the first value that will be generated for the column.
2. Increment: The value by which the identity column will increase for each new row inserted. The default value is 1.
3. Maximum: The maximum value that the identity column can hold. Once this value is reached, the identity column will no longer generate new values and will throw an error.
To alter the identity column in SQL Server 2008, follow these steps:
1. Open SQL Server Management Studio (SSMS): Launch SSMS and connect to your SQL Server instance.
2. Navigate to the Database and Table: Expand the database where your table resides, and then expand the table to which you want to make changes.
3. Right-click and Modify: Right-click on the identity column you want to alter and select “Properties” from the context menu.
4. Edit Identity Column Properties: In the “Column Properties” window, you will find the “Identity” section. Here, you can change the seed, increment, and maximum values for the identity column.
5. Change Seed: To change the starting value of the identity column, modify the “Seed” field and enter the desired value.
6. Change Increment: To change the increment value, modify the “Increment” field and enter the new value. If you want to reset the increment to the default value of 1, simply leave this field blank.
7. Change Maximum: To change the maximum value, modify the “Maximum” field and enter the new value. If you want to remove the maximum value constraint, enter “NULL” in the field.
8. Apply Changes: Once you have made the necessary changes, click “OK” to apply the alterations to the identity column.
9. Test the Changes: After applying the changes, it is crucial to test the new identity column values to ensure that they meet your requirements. Insert new rows into the table and verify that the identity values are generated as expected.
By following these steps, you can successfully alter the identity column in SQL Server 2008. Always remember to back up your database before making structural changes to ensure data integrity and avoid potential issues.
