How to Alter Column to Add Identity in SQL Server
In SQL Server, adding an identity column to an existing table is a common task when you need to generate unique identifiers for new rows. An identity column is a special type of column that automatically generates a unique number for each new row. This article will guide you through the steps to alter a column to add identity in SQL Server.
First, you need to identify the table where you want to add the identity column. Once you have the table name, follow these steps:
1. Open SQL Server Management Studio (SSMS) and connect to your database.
2. In the Object Explorer, navigate to the database where your table is located.
3. Right-click on the table and select “Design” to open the table in Design view.
Now, let’s proceed with adding the identity column:
1. In Design view, click on the column where you want to add the identity property.
2. In the Properties window, locate the “Identity” property. By default, it should be set to “False.”
3. Change the “Identity” property to “True.” This will enable the identity column for the table.
Next, you need to set the identity properties for the column:
1. In the Properties window, find the “Identity Seed” property. This value represents the starting number for the identity column.
2. Set the “Identity Seed” property to the desired starting number. For example, if you want the identity column to start at 1, set this value to 1.
3. Find the “Identity Increment” property. This value represents the increment between each new identity value.
4. Set the “Identity Increment” property to the desired increment value. For example, if you want the identity column to increment by 1 for each new row, set this value to 1.
After setting the identity properties, you can add the identity column to the table:
1. Save the changes to the table in Design view.
2. Right-click on the table and select “Save Table As” to save the changes to the database.
Now, the table should have an identity column with the specified properties. When new rows are inserted into the table, the identity column will automatically generate unique values for each row.
It’s important to note that adding an identity column to an existing table can have implications on the existing data. Make sure to review the data and consider any potential issues before proceeding with the alteration.
In conclusion, adding an identity column to an existing table in SQL Server is a straightforward process. By following the steps outlined in this article, you can easily alter a column to add identity and ensure that each new row has a unique identifier.
