DBI202Xuất hiện trong 2 đề thi
Suppose relation R1(A, B) has the following tuples: | A | B | | :--- | :--- | | 1 | a | | 2 | b | | 3 | c | | 4 | d | | 5 | e | and the relation R2(C, A) has the following tuples: | C | A | | :--- | :--- | | 101 | 1 | | 102 | 2 | | 103 | 3 | | 104 | 1 | | 105 | 1 | Which tuple is contained in the result of the following query: ```sql SELECT R1.B, R2.C FROM R1 RIGHT JOIN R2 ON R1.A = R2.A; ```
Các lựa chọn
A(a, 101); (a, 104); (a, 105); (b, 102); (c, 103); (d, NULL); (e, NULL)
B(a, 101); (b, 102); (c, 103); (a, 104); (a, 105)
C(a, 101); (b, 102); (c, 103)
D(a, 101); (a, 104); (b, 102); (c, 103); (e, NULL)