27.何者並非關連式代數(Relational Algebra)中的關連運算子(Relational Operator)?
(A)限制(Restrict)
(B)投影(Project)
(C)聯集(Union)
(D)差集(Difference)
(E)加法(Add)

答案：登入後查看
統計： A(0), B(2), C(0), D(0), E(2) #2492612