First page Back Continue Last page Graphics
Third Normal Form
Decomposition into 3NF
3NF Decomposition Algorithm
- Decomposition is lossless join
- Lossless join decomposition
- A decomposition {R1, R2} is a lossless-join decomposition
if R1 R2 R1 or R1 R2 R2
- Idea:
- A candidate key (K) is in one of the relations Ri in decomposition (last step of algorithm guarantees this)
- Closure of candidate key under Fc must contain all attributes in R (definition of candidate key)
- Follow the steps of attribute closure algorithm (Fig. 7.7)
to show that the sufficient lossless join condition is satisfied for K+. (details omitted)
Notes: