In a relational data model, which one of the following statements is TRUE?
A.
A relation with only two attributes is always in BCNF.
B.
If all attributes of a relation are prime attributes, then the relation is in BCNF.
C.
Every relation has at least one non-prime attribute.
D.
BCNF decompositions preserve functional dependencies.
Solution:
Option A: True
Option B: False, consider the Relation R(A, B, C, D) with all prime attributes and have functional dependencies below:
From the FD, 'C' is not the super key, which is not allowed in BCNF.
Option C: False, consider the above relation R, all attributes are prime.
Option D: False, lossless join is possible in BCNF, but dependency preserving is not possible.