Project ForgeConsider a Suppliers(sid,sname,city,street) relation. Assume that each supplier and each street within a city has a unique name, and (sname,city) forms a candidate key. No other functional dependencies are implied other than those implied by primary and candidate keys. Which one of the following is TRUE about the above schema?
- The schema is in BCNF.
- BThe schema is in 3NF but not in BCNF.
- CThe schema is in 2NF but not in 3NF.
- DThe schema is not in 2NF.
Explanation
Candidate keys are {sid} and {sname,city}; the only non-prime attribute is street. The two functional dependencies are sid->(sname,city,street) and (sname,city)->(sid,street), both with a superkey on the left — every determinant is a superkey, so the schema is in BCNF (and trivially 2NF/3NF too, since street's only dependency is on a whole key, never a partial one).
Source: GATE CS 2009 (2009)
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