DBI202Xuất hiện trong 1 đề thi
The functional dependency $A \to B$ for relation schema $R(A,B,C,D)$ implies that
Các lựa chọn
Ano two tuples in R can have the same value for attribute B
Bno two tuples in R can have the same value for attribute A
Cany two tuples in R that have the same value for B must have the same value for A
Dany two tuples in R that have the same value for A must have the same value for B