Delete Primary Keys
You can delete (drop) a primary key in SQL Server 2016 by using SQL Server Management Studio or Transact-SQL. When the primary key is deleted, the corresponding index is deleted.
To delete a primary key constraint using Object Explorer
In Object Explorer, expand the table that contains the primary key and then expand Keys.
Right-click the key and select Delete.
In the Delete Object dialog box, verify the correct key is specified and click OK.
To delete a primary key constraint using Table Designer
In Object Explorer, right-click the table with the primary key, and click Design.
In the table grid, right-click the row with the primary key and choose Remove Primary Key to toggle the setting from on to off.
To undo this action, close the table without saving the changes. Deleting a primary key cannot be undone without losing all other changes made to the table.
On the File menu, click Save table name.
To delete a primary key constraint
In Object Explorer, connect to an instance of Database Engine.
On the Standard bar, click New Query.
Copy and paste the following example into the query window and click Execute. The example first identifies the name of the primary key constraint and then deletes the constraint.
USE AdventureWorks2012; GO -- Return the name of primary key. SELECT name FROM sys.key_constraints WHERE type = 'PK' AND OBJECT_NAME(parent_object_id) = N'TransactionHistoryArchive'; GO -- Delete the primary key constraint. ALTER TABLE Production.TransactionHistoryArchive DROP CONSTRAINT PK_TransactionHistoryArchive_TransactionID; GO