更多"[单选题]The entity-relationship（E-R）da"的相关试题:
[单选题]The entity-relationship（E-R）data model is based on a perception of a real world that consists of a clletion 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 asetof（请作答此空）:A relationship isan association among several entities.The set of all entities of the same type and the set of all relationships of the ametype are termed an entity sct 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 fllowing components:（ ）represent entity set,（ ）represent atributes,ete.In addition to entities and relations,the E-R model represents certain（ ）to which thecontents of a database must conform.The entity-relationship model is widely used in database design.
A.keys
B.attributes
C.records
D.Rows
[单选题]English course objectives at the stage of basic education include five aspects, that is,students' language skills, language knowledge, emotional attitude, cultural awareness and__________.
A.learning level
B.practical activities
C.learning strategies
D.habits of thinking
[单选题]D.evelopment teams often behave much like baseball or basketball teams.Even though they may have multiple specialties,all the members work toward（ ）.However,on systems maintenance and enhancement teams,the engineers often work relatively independently,much like wrestling and track teams.
A team is（ ）just a group of people who happen to work together.Teamwork takes practice and it involves special skills.Teams require common processes;they need agreed-upon goals;and they need effective guidance and leadership.The methods for guiding and leading such teams are well known,but they are not obvious.
A.convenient
B.existing
C.practical
D.real
[单选题]数据流程图（Data Flow Diagram，DFD/Data Flow Chart）是描述系统数据流程的工具。它将数据独立抽象出来，通过图形方式描述信息的来龙去脉和实际流程。在数据流程图中用（ ）表示处理过程。
A.长方形
B.带圆角的长方形
C.正方形
D.圆或椭圆
[单选题]某企业内部两栋楼之间距离为350米，使用62.5/125 u m多模光纤连接。100Base-FX 连接一切正常，但是该企业将网络升级为1000Base- FX后，两栋楼之间的交换机无法连接。经测试，网络链路完全正常，解决此问题的方案是（ ）。
A.把两栋楼之间的交换机模块更换为单模模块
B.把两栋楼之间的交换机设备更换为路由器设备
C.把两栋楼之间的多模光纤更换为50/125 u m多模光纤
D.把两栋楼之间的多模光纤更换为8/125 u m单模光纤
[单选题]变量W_data定义如下：union data_node{float ff'int n;char ch;}W_data;则变量W_data所占的内存存储空间可表示为______。
A.sizeof（int）
B.sizeof（char）
C.sizeof（float）
D.sizeof（int）+sizeof（char）+sizeof（float）
[单选题]This model embodies many new features.
A.resists
B.includes
C.makes up
D.marks
[单选题]The Project Management Triangle is a model of the constraints of projectmanagement.These constraints have been listed scope(or quality),（73）,and cost.
A.resource
B.time
C.plan
D.tool
[单选题]The spiral model is a software development model combining elements of both ( ) and prototyping-in-stages, so it's a healthy mix of top-down and bottom-up concepts。
A.design
B.progam
C.coding
D.plan
[单选题]The first P in the PPP teaching model stands for __________ , which aims to get learners to perceive the form and meaning of a structure.
A.practice
B.production
C.presentation
D.preparation
[单选题]（ ） is used to model aggregates of information and the relationships these aggregates have to other.
A.Dat
A.flow diagram
B.Entity relationship diagram
C.Sequence diagram
D.Structure diagram
