【简答题】将学生表的“年龄”属性限制在18~22之间,这属于( )。 A)实体完整性规则 B)参照完整性规则 C)域完整性规则 D)字段限制规则
【判断题】实验动物设施周围应无传染源,不得饲养非实验用家畜家禽。
【简答题】关系的实体完整性规则定义了( )不能取空值。
【单选题】在阐述竞争优势的时候要着重说明产品的()或竞争优势和策略。
【单选题】What does Ron Arkin think of WL-16?
A.
He doesn't think it is useful.
B.
He thinks it is only a manipulator.
C.
He thinks it is user-friendly.
D.
He is unsure of its safety.