Primary keys – the basics
Single-column primary keys
Multi-column primary keys
NOT NULL
Instruction
All right. As you can see, it's possible, but inadvisable, to use a varchar column as the primary key.
Primary keys are important, so we mark which column the primary key is in ERD diagrams too. We usually use the abbreviation PK.
Exercise
Try to create the database using the following ERD:
Stuck? Here's a hint!
Type:
CREATE TABLE account ( user_id integer PRIMARY KEY, first_name varchar(32), nickname varchar(24), description varchar(64) );
