ssd7 所有选择题ssd 所有选择题ssd7 所有选择题ssd7 所有选择题.doc

1. In the Entity-Relationship model, the degree of a relationship specifies which of the following? (a) The cardinality ratio of the relationship (b) The number of integrity constraints required to implement the relationship (c) The number of attributes that characterize the relationship (d) The number of entities that participate in the relationship Correct answer is (d) -------------------------------------------------------------------------------- 2. In an ER model, which of the following is true about a component attribute? (a) A component attribute is always atomic. (b) Component attributes must always be combined by an aggregation operation. (c) A component attribute can be a composite attribute. (d) A component attribute always contains other components. Correct answer is (c) -------------------------------------------------------------------------------- 3. In the Entity-Relationship model, properties that characterize entities and relationships are modeled as (a) attributes (b) participation constraints (c) entity types (d) weak entities Correct answer is (a) -------------------------------------------------------------------------------- 4. What is an identifying owner in an ER model? (a) The entity upon which a weak entitys existence depends (b) The relationship that identifies a weak entitys owner (c) The entity upon which a strong entitys existence depends (d) The relationship that identifies a strong entitys owner Correct answer is (a) -------------------------------------------------------------------------------- 5. In an ER model, the cardinality ratio of a relationship type is (a) the number of instances of relationships of that relationship type (b) the number of entity types involved in that relationship type (c) the number of relationships of that relationship type in which an entity can participate (d) the minimum number of entities that can participate in that relationship typ