DBI202Xuất hiện trong 1 đề thi
When we apply set operators (UNION, INTERSECT, EXCEPT) to two relations R and S, which conditions on R and S must be satisfied?
Các lựa chọn
AR and S must have schemas with identical sets of attributes and the types (domains) for each attribute must be the same in R and S
BBefore we compute the set-theoretic union, intersection, or difference of sets of tuples, the columns of R and S must be ordered so that the order of attributes is the same for both relations
CAll of the others