Primary Key Question Explained
This worked SQL Fundamentals practice question tests Schema Design. Try the answer first, then review why A is the best choice.
Short answer
The correct answer is A. A column or columns that uniquely identify each row.
A primary key enforces row identity. It must be unique and not null, but it does not have to be named id. The key is to match the exact action in the prompt to the tool, command, or concept that performs that action directly. Here, A. A column or columns that uniquely identify each row is the only option that satisfies the scenario without adding unrelated behavior.
Practice Question
What is a primary key?
Why A is correct
A primary key enforces row identity. It must be unique and not null, but it does not have to be named id. The key is to match the exact action in the prompt to the tool, command, or concept that performs that action directly. Here, A. A column or columns that uniquely identify each row is the only option that satisfies the scenario without adding unrelated behavior.
Why the other options are wrong
Option B does not match the requirement in the prompt. The correct answer is A because A primary key enforces row identity. It must be unique and not null, but it does not have to be named id.
Option C does not match the requirement in the prompt. The correct answer is A because A primary key enforces row identity. It must be unique and not null, but it does not have to be named id.
Option D does not match the requirement in the prompt. The correct answer is A because A primary key enforces row identity. It must be unique and not null, but it does not have to be named id.
Key idea: Schema Design
Schema Design questions test whether you can connect a common workflow problem to the right practical command, service, or concept. Instead of memorizing isolated definitions, look for the job being done in the prompt: staging a file, querying rows, running code, persisting container data, checking a service, or choosing the right cloud building block. The best answer usually names the simplest tool that performs that job directly. For SQL Fundamentals, the safest study pattern is to read the scenario, underline the action verb, and eliminate answers that solve a different problem. If an option sounds related but changes the scope, adds risk, or describes a different layer of the stack, it is probably a distractor. After choosing an answer, explain why the other three fail; that habit builds the practical judgment these quizzes are meant to measure.
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Quick FAQ
What is the correct answer for this SQL Fundamentals question?
The correct answer is A. A column or columns that uniquely identify each row. A primary key enforces row identity. It must be unique and not null, but it does not have to be named id. The key is to match the exact action in the prompt to the tool, command, or concept that performs that action directly. Here, A. A column or columns that uniquely identify each row is the only option that satisfies the scenario without adding unrelated behavior.
How should I study similar SQL Fundamentals questions?
Review the explanation, compare every distractor, then practice related questions in the same domain: Schema Design.