Are you facing a situation where you need to drop a primary key on a table in SQL Server, but you don’t know which constraint is associated with it? Don’t worry, there is a way to drop the primary key without specifying the constraint. Let’s explore how to do it.

Let’s consider a scenario where you have a table with four columns: SrNo, NodeID, EnrollmentNo, and FingerNo. The NodeID and EnrollmentNo columns already have a primary key constraint, and now you want to add another primary key constraint on the FingerNo column as well.

To achieve this, you can follow these steps:

Using SQL Server 2000

1. Open Enterprise Manager.
2. Expand the server, database, and tables.
3. Right-click on the table name and select “Design Table”.
4. You will see all the columns in the table, including the existing primary key columns.
5. To add the FingerNo column to the primary key, first remove the “Allow Null” check on that column.
6. Press the control button and select all the columns you want to include in the primary key (including the previous primary key columns).
7. Right-click on the selected columns and choose “Set Primary Key”.
8. Save the table.

To verify if the primary key now includes the new column, you can refresh the database, open the table in design mode, and check the primary key configuration.

Using SQL Server 2005

1. Expand the server, database, tables, and keys.
2. Right-click on the key name and select “Modify”.
3. Follow the same process as in SQL Server 2000: uncheck the “Allow Null” option on the FingerNo column, select all the columns you want in the primary key, and right-click to set the primary key.
4. Save the changes.

It’s important to note that if you are using certain data types like varchar(max), text, ntext, or nvarchar(max), you may not be able to set them as part of the primary key. In such cases, try giving a fixed length to those columns, like varchar(100).

If you are unsure about the primary key constraint name or want to view all primary keys in the database, you can run the following script:

SELECT A.TABLE_NAME, A.CONSTRAINT_NAME, B.COLUMN_NAME
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS A, INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE B
WHERE CONSTRAINT_TYPE = 'PRIMARY KEY' AND A.CONSTRAINT_NAME = B.CONSTRAINT_NAME
ORDER BY A.TABLE_NAME

This script will provide you with the names of all primary key constraints in the database, along with the associated column information.

Remember, when creating a primary key, a clustered index is created by default. This means that the table on which you are creating the primary key will be unavailable for users until the process is complete. Make sure no users are connected to the database before making any changes.

We hope this guide helps you understand how to drop a primary key in SQL Server without specifying the constraint. If you have any further questions, feel free to ask in the comments below.

Happy coding!