Introduction
Primary keys
Foreign keys
Updating and deleting with foreign keys
Instruction
Perfect! When we add a primary key to a table, the database engine internally stores the primary key in a constraint object. By default, this object gets an auto-generated name, which we'll explain in a second. However, you can also specify your own name for a constraint. For instance, we have the following table:
CREATE TABLE tennis_court ( id integer, address text, type varchar(32) );
We can add a primary key with a custom name in the following way:
ALTER TABLE tennis_court ADD CONSTRAINT court_pk PRIMARY KEY (id);
The code above will add a primary key constraint with the custom name court_pk.
Exercise
Let's try to add the primary key to the project table again:
CREATE TABLE project ( id integer, name varchar(64), description text, manager_id integer );
Add a primary key constraint on the id column and give the constraint the name project_pk.
