- EER Diagram always produces the databases that are normalized.
- No redundancy of facts.
- No cluttering of facts.
- Must preserve information.
- Must preserve functional dependencies.
- Multi-value attributes.
- Values of attributes are pull from set of atomic values.
NF2 = Non First Normal Form
- How to enforce functional dependency.
- We use keys to enforce functional dependencies X->Y
- Non First Normal Forms Datastructures
- NF^2: Non First Normal Form
- 1NF: R is in 1NF iff all domain values are atomic.
- 2NF: R is in 2NF iff R is in 1NF and every non-key attribute is fully dependent on the key.
- 3NF: R is in 3NF iff R is in 2NF and every non-key attribute is non-transitively dependent on the key.
- BCNF (Boyce-Codd Normal Form): R is in BCNF iff every determinant is a candidate key.
- Determinant: A set of attributes on which some other attribute is fully functionally dependent.
All attributes must dependent on the key (1NF), the whole key (2NF), and nothing but the key (3NF), so help me codd!
- There does exist relations which can only be decomposed to 3NF, but not to BCNF, while being lossless and dependency preserving.
- It can only happen when the relation has overlapping keys.
- There does exists relations that exists in 3NF and not in BCNF. (Only in theory)