2. 计算机
  3. The entity-relationship (E-R) data model is based on a perception of a real world that consists of a collection of basic objects

The entity-relationship (E-R) data model is based on a perception of a real world that consists of a collection of basic objects

admin2020-08-10  49
问题 The entity-relationship (E-R) data model is based on a perception of a real world that consists of a collection of basic objects, called(71)，and of relationships among these objects. An entity is a “thing” or “object” in the real world that is distinguishable from other objects. Entities are described in a database by a set of (72) . A relationship is an association among several entities. The set of all entities of the same type and the set of all relationships of the same type are termed an entity set and relationship set, respectively. The overall logical structure (schema) of a database can be expressed graphically by an E-R diagram, which is built up from the following components: (73) represent entity set, (74) represent attributes, etc. In addition to entities and relations, the E-R model represents certain(75)to which the contents of a database must conform. The entity-relationship model is widely used in database design.
(74)
选项 A、rectangles
B、ellipses
C、diamonds
D、lines
答案B
解析
转载请注明原文地址:https://www.kaotiyun.com/show/q5TZ777K
本试题收录于： 数据库系统工程师上午基础知识考试题库软考中级分类
0

数据库系统工程师上午基础知识考试

软考中级

相关试题推荐
随机试题
最新回复(0)