Question at position 11 In ERDs, the primary key isAn attribute that cannot be modified after it is setAn attribute that uniquely identifies each record in a database tableA graphical symbol indicating the connection between entitiesA set of optional attributes linked to an entity

Question

BlackTom AI · Accepted Answer

In this question about ERDs, we need to evaluate what each option implies about the primary key.
Option 1: 'An attribute that cannot be modified after it is set' — This describes immutability, which is not the defining feature of a primary key. Primary keys can be updated in some systems, though it’s generally discouraged; the key point is uniqueness, not immutability. Thus this statement is misleading as a general definition.
Option 2: 'An attribute that uniquely identifies each record in a database table' — This accurately captures the core purpose of a primary key: to provide a unique identifier for every row in a table. This aligns with standard database design concepts in ER modeling, where the primary key ensures entity instances are distinguishable.
Option 3: 'A graphical symbol indicating the connection between entities' — In an ER diagram, connections between entities are represented by relationships lines and symbols, not by the primary key itself. This option confuses the visual representation with the functional role of a primary key, making it incorrect.
Option 4: 'A set of optional attributes linked to an entity' — Primary keys are typically a single attribute (or a specific combination of attributes, i.e., a composite key) that uniquely identifies a record, not merely a set of optional attributes. This misstates both the uniqueness requirement and the notion of optional attributes.
Overall, option 2 provides the precise definition of a primary key, while the other options describe related but incorrect aspects or misconceptions about keys in ER diagrams.

Question at position 11 In ERDs, the primary key isAn attribute that cannot be modified after it is setAn attribute that uniquely identifies each record in a database tableA graphical symbol indicating the connection between entitiesA set of optional attributes linked to an entity

查看解析

登录即可查看完整答案

类似问题

A primary unique key:

What role does a primary key play in a database?

In RDBMS, what is a primary key?

What does `PRIMARY KEY` in a table ensure?

How many primary keys can a table have?

What is a primary key?

A database table usually has a(n) _______________________ that uniquely identifies each row in the table.

更多留学生实用工具

考试浏览器助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单