Normalization
From Wiki Notes @ WuJiewen.com, by Jiewen Wu
Functional Dependency (FD)
A FD, an integrity constraint, on a relation scheme R is a constraint X->Y, where X and Y are sets of attributes. For a pair of tuple t and s, they satisfies the above FD if they agree on all attributes in Y whenever they agree on all attributes in X.
Some properties of FDs.
- Trivial (Reflexive) FDs: X->Y if Y is a subset of X.
- Augmentation: if X->Y then XZ->YZ
- Transitivity: if X->Y and Y->Z, then X->Z.
- Union: if X->Y and X->Z, then X->YZ.
- Decomposition: if X->YZ, then X->Y and X->Z.