In a relational database, which of the following about Primary Key is FALSE

Question

BlackTom AI · Accepted Answer

A primary key is a column (or combination of columns) that uniquely identifies each row in a table; it must be unique and cannot contain NULL values.

1) Relevant knowledge points and concepts
- Uniqueness: primary key values must be unique for each row.  
- Not-null: primary key columns cannot be NULL (they are mandatory).  
- Data type: there is no requirement that a primary key be an integer; it can be any suitable data type (VARCHAR, UUID, composite columns, etc.).  
- Composite keys: a primary key can consist of multiple columns.  
- Surrogate vs. natural keys: integers are commonly used as surrogate keys (AUTO_INCREMENT) for convenience, but they are not mandatory.

2) Step-by-step reasoning
- Examine each option against the definition and constraints of a primary key.
- Option "Primary key is used to identify a unique row in a table": matches the core definition (true).
- Option "Primary key is used to identify a unique record in a database": interpreted as identifying a unique record (row) — this is functionally true (primary key uniquely identifies records in its table).
- Option "Primary key must be an integer value": test this against examples and rules. Rules do not mandate integer type; many valid primary keys are strings (email), UUIDs, or composites (first_name + dob) — so this is false.
- Option "Primary key is a mandatory (must have) column in a table": primary key columns cannot be NULL, so they are mandatory — true.

3) Intermediate examples (illustrative)
- VARCHAR primary key: CREATE TABLE users (email VARCHAR(255) PRIMARY KEY); valid.
- UUID primary key: id UUID PRIMARY KEY; valid.
- Composite key: PRIMARY KEY (country_code, passport_number); valid.

4) Why the correct answer is correct
"Primary key must be an integer value" is false because SQL and relational theory impose uniqueness and non-null constraints, not a specific data type. Integers are common but not required.

5) Why other options are incorrect/ rejected
- Options 1 and 4 are correct statements about primary keys.  
- Option 2 is effectively correct in common usage (it identifies a unique record); any ambiguity does not make it false in the intended MCQ context.

6) Conclusion
The false statement is "Primary key must be an integer value", which matches the provided answer.

In a relational database, which of the following about Primary Key is FALSE单项选择题

类似问题

The table is the basic building block in database design. An attribute (or column) that uniquely identifies a particular object (or row) in the table is called:

If order_id is declared as a PRIMARY KEY, which of the following are guaranteed? Choose all that apply.

什么是主键？

Inspect the following conceptual model Identify the primary key of the Store entity

Each table in a relational database has one field designated as its primary:

Which of the following best describes the purpose of a primary key?

After transforming the above ERD to a Relational Schema, what is the primary Key for patient treatment?

A primary unique key:

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