Primary keys - the basics
Single-column primary keys
Multicolumn primary keys
Auto-increment columns and sequences
Instruction
Excellent! Now, you may wonder if the primary key must always be an integer column. The answer is no. You can choose other column types as well. For instance, you could give up the id column in our movie table and use the title of the movie as the primary key.
Are such solutions popular? Well, not really. Such a primary key will work more slowly and is more difficult to handle.
Exercise
Let's experiment. Create the table movie WITHOUT the id column. Put the following columns:
titlewhich is a field of up to 64 characters and the primary key,-
yearwhich is an integer and genrewhich is a text of up to 10 characters.
Stuck? Here's a hint!
Type
CREATE TABLE movie ( title varchar(64) PRIMARY KEY, year int, genre varchar(10) );
