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Suppose i have a table A which consists of only 1 candidate key

then what is true ?

If it is in 3NF, then it is also in BCNF or not ?

Garrick
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1 Answers1

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If it is in 3NF, then it is also in BCNF or not ?

Not necessarily. In general, 3NF states that there is no PFD (partial functional dependency) whereas BCNF states that there is no independent candidate key present. Means, even if there is multiple candidate key there will one super key and other keys will be a subset of the super key.

Since in your case, there is only one candidate key, I would say it's in both 3NF as well as BCNF since both the condition holds

X → Y is a trivial functional dependency (Y ⊆ X)

X is a super key for schema R

See Boyce–Codd normal form for more information

Community
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Rahul
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  • 2NF says there's no partial dependency. 3NF says there are no transitive dependencies. Your interpretation of what BCNF means looks wrong on the face of it. Informally, BCNF means that every arrow in a functional dependency is an arrow out of a candidate key. There can be more than one candidate key; they need not be subsets of a candidate key. (It's not clear to me whether you're saying that or not.) – Mike Sherrill 'Cat Recall' Sep 19 '16 at 16:45