Primary, unique, and key constraints

The following query creates a primary key for the id column:

CREATE TABLE IF NOT EXISTS products

(

  id INT UNIQUE AUTO_INCREMENT ,

  code INT NOT NULL ,

  name VARCHAR(25) NOT NULL ,

  quantity INT NOT NULL ,

  price DECIMAL(6,2) NOT NULL

) ;

So the question is does every unique column a primary key? No.

The reason is the primary key is a type of unique column. A more complete explanation is here.