Decomposition of a BCNF Relation
Suppose that we choose { SDP, CSJDQV }. This is in BCNF, and there is no reason to decompose further
However, suppose that these queries are important:
- Find the contracts held by supplier S.
- Find the contracts that department D is involved in.
Decomposing CSJDQV further into CS, CD and CJQV could speed up these queries. (Why?)
On the other hand, the following query is slower:
- Find the total value of all contracts held by supplier S.