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A quick question.  Why do you need a movies-actors table on page 174 (Chapter 6)?  Why can't actors have one to many relationship with movies just as directors have, requiring only 3 tables in the cinema database. 

Thx!

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Good question! Actors have a many-to-many relationship with movies because each actor can be in multiple movies and each movie has multiple actors. A rule in this model is that each movie only has a single director, so there's a one-to-many relationship between directors and movies (although in real life some movies have more than one director these days). 

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