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Given $R$=($A,B,C,D,E,G$), And $F_c$={$A$$\rightarrow$$E$ ,$E$$\rightarrow$$ACD$ ,$BD$$\rightarrow$$E$, $CD$$\rightarrow$$B$}

Candidate keys are: $GA, GE, GDB, GCD$

Lets say I pick the FD $A$$\rightarrow$$E$ that violates BCNF
(1) should the decomposition looks like that:

$R_2$=$(A,G)$, $R_1$=$(A,E,C,D,B)$ // [$R_1$ is created by $A$ and due to $E$$\rightarrow$$ACD$ and $CD$$\rightarrow$$B$ ]

(2) or perhaps like that:

$R_1$=$(A,E)$, $R_2$=$(A,B,C,D,G)$

I am struglling to realize which decomposition is correct cause according to the algorithm you should take the FD $X$$\rightarrow$$Y$ that violates the BCNF and decomposite it to relations such that $R_1$=$XY$ and $R_2$=$R-Y$

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1 Answer 1

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The first is the correct decomposition since from X -> Y one should decompose R in X+, the closure of X (that is AECDB) and T - (X+ - X) (that is AG), where T is the set of all the attributes.

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