I have been following the book of sitepoint php and mysql novice to ninja , implementing all examples , everything was running smooth, until chapter 7, final topic managing jokes , where the author states that the database example in the chapter CMS was not designed to support add jokes and delete jokes operation. What is bugging me is, why is it not suitable for these operations, it seems normalized with no database anomalies.

Jokes
Id
Joketext
Jokedate
Authorid

Jokecategories
Jokeid
Categoryid

Categories
Id
Name

Author
Id
Name
Email

Any help and reply would be much appreciated

Thanks,
T.