代写 R Exercise 1

Exercise 1
Consider a relation with schema R (A, B, C, D) and FDs the set F:
F= {
AB→C
C→D
D→A }

• (10%) Find all the candidate keys of R. 

• (5%) Indicate all BCNF violations for R. 

• (10%) Decompose the relations into collections of relations that are in BCNF. 

• (5%) Indicate which dependencies, if any, are not preserved by the BCNF decomposition. 


Exercise 2
Consider a relation with schema R (A, B, C, D) and FDs the set F:
F ={ A→B
A→C
C→D }

• (5%) Determine the set of all candidate keys for the relation schema. 

• (5%) Determine the highest normal form (no NF, 1NF, 2NF, 3NF, BCNF) that the relation 
schema is in. Explain your answer. 

• (10%) Decompose the relation schema into new relation schemas that satisfy the next higher 
normal form. 

• (10%) Show the minimal covers of functional dependencies for the decomposed relation 
schemas. 

• (10%) List the candidate keys of the decomposed relation schemas. 

• (10%) Prove that the decomposition is a lossless join decomposition and/or dependency 
preserving.