Consider a decomposition R 1 ,...,R of R obtained through 3NF synthesis. Suppose that Ri is not in BCNF and let X ? A be a violating FD in Ri. Prove that Ri must have another FD, Y ? B, which will be lost if Ri is further decomposed with respect to X ? A.
What will be an ideal response?
If X ? A is a violating FD of Ri, there must be a key K in Ri and an FDK ? B in the minimal cover, such that A ? K , X ? K ,and B ? K. Since the decomposition with respect to X ? A splits the attributes of K between the schemas XA and Ri ? A, where Ri is the set of attributes of Ri, the FDK ? B is not embedded in any schema.
If it were possible to derive K ? B using the remaining FDs, then it would mean that K ? B is redundant, contrary to the fact that it was chosen from a minimal cover.
You might also like to view...
When a style is set to update automatically, you can modify the style by formatting the text directly
Indicate whether the statement is true or false
Which of the following is true about SSL?
A. it uses shared-key encryption only B. it uses sockets to communicate between client and server C. it operates at the Data Link layer D. it uses IPsec to provide authentication