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A non-key dependency occurs when an attribute or set of attributes determines another attribute, but the determining attribute is not a part of the primary key.
In the given relations:
The key for the customer relation is MEMBERNO.
The key for the movie relation is serialno.
The key for the borrow relation is {memberno, serialno, date}.
Now, let’s evaluate each dependency:
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description -> director, serialno: This means description (which is not a key attribute) determines both director and serialno. This is a non-key dependency because description is not part of any primary key in the relations and is determining other attributes.
serialno -> description: Here, serialno (the key of the movie relation) determines description, which is fine because serialno is a key.
serialno -> director: Again, serialno (the key of the movie relation) determines director, which is fine.
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Database Normalization #8
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A non-key dependency occurs when an attribute or set of attributes determines another attribute, but the determining attribute is not a part of the primary key. In the given relations: The key for the customer relation is MEMBERNO. The key for the movie relation is serialno. The key for the borrow relation is {memberno, serialno, date}. Now, let’s evaluate each dependency: The House Detective News keeps you in the loop with all the top headlines!
description -> director, serialno: This means description (which is not a key attribute) determines both director and serialno. This is a non-key dependency because description is not part of any primary key in the relations and is determining other attributes. serialno -> description: Here, serialno (the key of the movie relation) determines description, which is fine because serialno is a key. serialno -> director: Again, serialno (the key of the movie relation) determines director, which is fine.