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What are set of FDs for the relation in DBMS?


joined on
September 16,2014
Asked on January 03,2015
Consider the following set of FDs for the relation R(A, B, C, D, E):
F= {A-->B, AB-->C, D-->AC, D-->E}
F'= {A-->BC, D-->AE}
Check whether these are equivalent sets.
joined on
October 10,2013
Replied on January 04,2015

A-->B means A functionally defines B.
AB-->C means A and B functionally defines  C
D--> AC means D functionally defines A and C
D--> E means D functionally defines E

If understand the properties of functional dependency as given below

1. Reflexivity: If Y ⊆ X, then X → Y
2. Augmentation: If X → Y , then XZ → Y Z
3. Transitivity: If X → Y and Y → Z, then X → Z
4. Union: If X → Y and X → Z, then X → Y Z
5. Decomposition: If X → Y Z, then X → Y and X → Z
6. Pseudotransitivity: If X → Y and W Y → Z, then W X → Z
7. Composition: If X → Y and Z → W, then XZ → Y W 

And find the minimal cover,

we can get 

A-->BC, D-->AE

So F and F' are same.

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