CP363 Lecture Notes - Lecture 22: Functional Dependency
8 Apr 2019
School
Department
Course
Professor
Document Summary
Any fd produced by reflexive property is always trivial, not included in f+ F = {a b, b c} A+ = {a, b, c} (because lhs was part of current a+) A+ w. r. t f+ will give same result. F+ = {a b, b c, a c (transitivity), ac bc (augmentation by c), ab ac (augmentation by a), ab bc (augmentation by b of a c)} Also a key (set of all attributes is always a key) Does order matter? idk i missed it ?? but probably not. Two sets of fds f and g are equivalent if: Every fd in f can be inferred from g, and. Every fd in g can be inferred from f. Hence, f and g are equivalent if f+ = g+ F covers g if every fd in g can be inferred from f. F and g are equivalent if f covers g and g covers f.
