A _____________ constraint requires that an entity belong to no more than one lower-level entity set.
A. Disjointness
B. Uniqueness
C. Special
D. Relational
Answer:A
A _____________ constraint requires that an entity belong to no more than one lower-level entity set.
A. Disjointness B. Uniqueness C. Special D. Relational
Explanation:For example, student entity can satisfy only one condition for the student type attribute; an entity can be either a graduate student or an undergraduate student, but cannot be both.