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#1 DecafJava  Icon User is offline

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A relational scheme in BCNF or 3NF

Post icon  Posted 08 July 2009 - 08:34 PM

Say I have a relationship:

ACTORS----<play in>-----MOVIES
...where one actor can play in many movies and one movie can have many actors (many-to-many)

So I am trying to do an analysis on whether this relationship is in BCNF or 3NF form.

the table: play(actor_id, movie_id)
with the: superkey->{actor_id, movie_id}

Seems to not have any functional dependency. So what can you conclude? If it's neither BCNF of 3NF, any suggestions on how to modify it to make it either BCNF or 3NF?

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Replies To: A relational scheme in BCNF or 3NF

#2 crcapps  Icon User is offline

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Re: A relational scheme in BCNF or 3NF

Posted 09 July 2009 - 06:51 AM

View PostDecafJava, on 8 Jul, 2009 - 07:34 PM, said:

Say I have a relationship:

ACTORS----<play in>-----MOVIES
...where one actor can play in many movies and one movie can have many actors (many-to-many)

So I am trying to do an analysis on whether this relationship is in BCNF or 3NF form.

the table: play(actor_id, movie_id)
with the: superkey->{actor_id, movie_id}

Seems to not have any functional dependency. So what can you conclude? If it's neither BCNF of 3NF, any suggestions on how to modify it to make it either BCNF or 3NF?



Pretty much any 3NF is also BCNF. Since you only have 2 relvars, and neither depend on another, non-key field, I would say BCNF. If it was, for example play(actor_id, movie_id, movie_type) where movie_id implied movie_type, but movie_type was not unique, then it would be 3NF but not BCNF
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#3 DecafJava  Icon User is offline

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Re: A relational scheme in BCNF or 3NF

Posted 09 July 2009 - 05:35 PM

Thanks!
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