In a relational database management system, what is a foreign key?

Question

BlackTom AI · Accepted Answer

Reiterating the question to set the stage: In a relational database management system, what is a foreign key? Then, we evaluate each answer option to see which description matches the standard definition and role of a foreign key.
Option a: 'A field that must have a unique value.' This describes a candidate key or possibly a primary key, not specifically a foreign key. A field with unique values is important for identifying records, but uniqueness alone does not define a foreign key relationship between tables.
Option b: 'A foreign key is the same as a primary key.' This is a common misconception. A foreign key is not the same as a primary key; the primary key uniquely identifies a row within its own table, while a foreign key establishes a link to a primary key (or candidate key) in another table. They serve related but distinct roles in referential integrity.
Option c: 'A field that is an auto number data type.' An auto-number (or auto-increment) field is often used for primary keys or surrogate keys, but it does not describe a foreign key. A foreign key can reference an auto-incremented primary key, but the key concept of a foreign key is about referential linking, not the data type alone.
Option d: 'A field in one table that is the primary key in another table.' This statement captures the essential mechanism of a foreign key: it is a field in one table that references (points to) the primary key in another table, thereby creating a referential link between the two tables and enforcing relational integrity.
In summary, option d accurately describes a foreign key by emphasizing its role as a reference to a primary key in another table, which is the core concept underpinning relationships in relational databases. The other options either mischaracterize the key’s purpose or describe features not fundamental to foreign keys, such as uniqueness, type, or equality to a primary key. The misinterpretations could lead to confusion about how tables are related and how constraints ensure data consistency across the schema.

In a relational database management system, what is a foreign key?单项选择题

类似问题

什么是外键？

In a Database a column or columns used to uniquely identify a row from another table is known as

A foreign key in a relational schema is based on ________ in ERD?

.... is the primary key of another entity to which an entity has a relationship.

更多留学生实用工具

智能学习助手

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