The entity-relationship(E-R)data model i

免费题库2022-08-02 26

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（　　）,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（　　）.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:（　　）represent entity set,（　　）represent attributes,etc.In addition to entities and relations,the E-R model represents certain（　　）to which the contents of a database must conform.The entity-relationship model is widely used in database design.问题1选项A.dataB.thingsC.entitiesD.objects问题2选项A.keysB.attributesC.recordsD.rows问题3选项A.rectanglesB.ellipsesC.diamondsD.lines问题4选项A.rectanglesB.ellipsesC.diamondsD.lines问题5选项A.thingsB.objectsC.conditionsD.constrains

选项

答案 CBABD

解析实体-关系（E-R）数据模型基于对现实世界的感知，该现实世界由一组基本对象（称为实体）和这些对象之间的关系组成。实体是现实世界中与其他对象相区别的“事物”或“对象”。实体在数据库中由一组属性描述。关系是几个实体之间的关联。同一类型的所有实体的集合和同一类型的所有关系的集合分别称为实体集和关系集。数据库的总体逻辑结构（设计）可以用E-R图图形化表示，E-R图由以下组件组成：矩形表示实体集，椭圆表示属性等。除了实体和关系之外，E-R模型还表示数据库内容必须符合的某些约束。E-R模型在数据库设计中得到了广泛的应用。

转载请注明原文地址:https://tihaiku.com/congyezige/2420025.html

本试题收录于：中级数据库系统工程师题库软件水平考试初中高级分类

中级数据库系统工程师

软件水平考试初中高级

相关试题推荐

随机试题

最新回复(0)

The entity-relationship(E-R)data model i

中级数据库系统工程师

软件水平考试初中高级