Discussion
A database of research articles in a journal uses the following schema.
(VOLUME, NUMBER, STARTPAGE, ENDPAGE, TITLE, YEAR, PRICE)
The primary key is (VOLUME, NUMBER, STARTPAGE, ENDPAGE) and the following functional dependencies exist in the schema.
(VOLUME, NUMBER, STARTPAGE, ENDPAGE) → TITLE
(VOLUME, NUMBER) → YEAR
(VOLUME, NUMBER, STARTPAGE, ENDPAGE) → PRICE
The database is redesigned to use the following schemas.
(VOLUME, NUMBER, STARTPAGE, ENDPAGE, TITLE, PRICE)
(VOLUME, NUMBER, YEAR)
Which is the weakest normal form that the new database satisfies, but the old one does not?
Answer: B
The weakest such normal form is 2NF.
In the old schema the key is (VOLUME, NUMBER, STARTPAGE, ENDPAGE), but YEAR depends on only part of it, (VOLUME, NUMBER). A non-prime attribute depending on part of a candidate key is a partial dependency, which violates 2NF. So the old database is in 1NF but not 2NF.
The redesign moves YEAR into (VOLUME, NUMBER, YEAR), where (VOLUME, NUMBER) is the whole key, removing the partial dependency. Both new schemas are in 2NF (in fact in BCNF, since every determinant is a key).
1NF holds for both, so it is not a difference. 3NF and BCNF are also met by the new design, but the question asks for the weakest form the new design gains, which is 2NF.
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