Database 1
Database Design
- Prof. dr. Paul M.E. De Bra
- Dept. of Computer Science
- Eindhoven Univ. of Technology
Canonical Cover Exercise
- Let {A,B,C,D,E} be the attributes of R and let F={AB, ABC, DEC, EBCD}. Compute Fc.
Completeness for Subset Constraints
- A relation scheme R satisfies the subset constraint Y X if and only if in for every instance r of R and AY and t1r BX and t2r such that t1(A)=t2(B). Prove that the following rules are complete for subset constraints:
- D1: if Y X then Y X
- D2: if Y X and Z is a set of attributes of R then YZ XZ
- D3: if Y X and Z Y then Z X
- Note that these rules closely resemble the Armstrong rules for functional dependencies. (use this similarity!)
Preparation for labsession 4
- Study chapter 7 of the database book, up to and including section 7.5.
- Section 7.4 explains (vertical) decomposition.
- Section 7.5 explains desirable properties of decomposition: the lossless-join property and the dependency preservation property.