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Schema Modification Approaches
Design “from scratch”:
- study the changed requirements;
- design the E-R schema again, the constraints, the translation to a relational scheme
- problem: the new relational scheme may be completely different from the original one
Adapt the design:
- undo some “decomposition” because of removed constraints;
- use new decomposition to ensure 3NF, BCNF or 4NF after adding the new constraints
Notes: