Why use an auto-incrementing primary key when other unique fields exist?

Question

I\'m taking a course called \"database systems\" and for our class project I have to design a website.

Here\'s an example of a table I created:

CREATE TA         


        

Answer 1

If the username is the primary key and a user changes his/her username, you will need to update all the tables which have foreign key references to the users table.