> You are well advised to choose a primary key that is not only unique, but also never changes during the lifetime of a table row. This is because foreign key c

> You are well advised to choose a primary key that is not only unique, but also never changes during the lifetime of a table row. This is because foreign key constraints typically reference primary keys, and changing a primary key that is referenced elsewhere causes trouble or unnecessary work. in one sense I agree with the author that things are generally just easier when you use surrogate primary keys, however they really should note here that the FOREIGN KEY constraint itself is not a problem at all as you can just use ON UPDATE CASCADE.