DBI202Xuất hiện trong 2 đề thi
Consider the relation $R(A,B,C,D)$ and functional dependencies: $A \to B$, $C \to D$. Find key of the above relation.
Các lựa chọn
AThe key is the A column
BThe key includes two columns $(A,C)$
CThe key is the A column or C column
DThe key is the C column