Which of the following is a characteristic of a foreign key?

Question

BlackTom AI · Accepted Answer

Question restatement: Which of the following is a characteristic of a foreign key?

Option 1: 'Must be unique' — This is incorrect. A foreign key is not required to be unique. In a child table, multiple rows can reference the same row in the parent table, so the foreign key values can repeat.

Option 2: 'Cannot be null' — This is not necessarily true. A foreign key column can be nullable, meaning a row may exist without a related row in the parent table, unless a NOT NULL constraint is explicitly applied.

Option 3: 'Is always a composite key' — This is false. A foreign key can consist of a single column or multiple columns (composite), but it is not required to be composite in all cases.

Option 4: 'Can contain duplicate values' — This is correct. Multiple child rows can reference the same parent row, so foreign key values may duplicate across rows in the child table. This reflects the many-to-one relationship from the child to the parent.

Additional clarification: The essential role of a foreign key is to enforce referential integrity by tying a column (or set of columns) in the child table to the primary key (or a candidate key) in the parent table. However, the exact constraints about uniqueness and nullability depend on how the key is defined and constrained in the schema.

Which of the following is a characteristic of a foreign key?

查看解析

登录即可查看完整答案

类似问题

If a 1:M relationship is mandatory on both sides, which of the following is true?

Why is a foreign key important in relational databases?

Referential integrity is enforced using:

A foreign key in one table must refer to:

Which of the following is NOT true about a foreign key that connects two tables in a database?

Which of the following is not a feature of a Foreign Key?

The FOREIGN KEY constraint should be added to which 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