SQL ALTER TABLE Add Primary Key
Example
ALTER TABLE EMPLOYEES ADD pk_EmployeeID PRIMARY KEY (ID)
This will add a Primary key to the table Employees on the field ID. Including more than one column name in the parentheses along with ID will create a Composite Primary Key. When adding more than one column, the column names must be separated by commas.
ALTER TABLE EMPLOYEES ADD pk_EmployeeID PRIMARY KEY (ID, FName)
