Settling for 3NF vs BCNF
CSJDPQV can be decomposed into SDP and CSJDQV, and both relations are in BCNF. (Which FD suggests that we do this?)
- Lossless decomposition, but not dependency-preserving.
- Adding CJP makes it dependency-preserving as well.
Suppose that this query is very important:
- Find the number of copies Q of part P ordered in contract C.
- Requires a join on the decomposed schema, but can be answered by a scan of the original relation CSJDPQV.
- Could lead us to settle for the 3NF schema CSJDPQV.