DBI202Xuất hiện trong 1 đề thi
Consider a relation $R(A, B, C, D, E, F)$ with FDs $\{AB \to C,\ C \to D,\ D \to A,\ D \to E\}$. Which of the following is the closure of $\{B,D\}$?
Các lựa chọn
A$\{ABCDE\}$
B$\{BCDE\}$
C$\{ABDEF\}$
D$\{ABCEF\}$
E$\{BCEF\}$