DBI202Xuất hiện trong 1 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