Summary of Database Tuning
The conceptual schema should be refined by considering performance criteria and workload:
- May choose 3NF or lower normal form over BCNF.
- May choose among alternative decompositions into BCNF (or 3NF) based upon the workload.
- May denormalize, or undo some decompositions.
- May decompose a BCNF relation further!
- May choose a horizontal decomposition of a relation.
- Importance of dependency-preservation based upon the dependency to be preserved, and the cost of the IC check.
- Can add a relation to ensure dep-preservation (for 3NF, not BCNF!); or else, can check dependency using a join.