Q 12: Which query returns only people who are BOTH Engineer AND Researcher?

Question

BlackTom AI · Accepted Answer

Using multiple labels in a pattern requires the node to carry every listed label; the pattern (p:Engineer:Researcher) matches only nodes that have both labels.

Relevant concepts:
- In Cypher, the syntax (n:Label) matches nodes with that label.
- Multiple labels in a single pattern, (n:LabelA:LabelB), mean the node must have LabelA AND LabelB.
- The boolean label test p:Label can also be used in WHERE (e.g., WHERE p:Label returns true if the node has that label).
- OR and AND in WHERE control logical combination of those boolean tests; commas are not valid for combining conditions.

Step-by-step reasoning:
1. Interpret the candidate queries:
   - MATCH (p:Engineer:Researcher) RETURN p; directly expresses the requirement: nodes labeled both Engineer and Researcher.
   - MATCH (p) WHERE p:Engineer OR p:Researcher RETURN p; uses OR, so it returns nodes that are Engineer OR Researcher (includes nodes with only one of the labels).
   - MATCH (p:Person) WHERE p:Engineer, p:Researcher RETURN p; uses a comma in WHERE which is invalid Cypher syntax; the intent might have been to require both, but this is not correct syntax.
   - MATCH (p:Engineer OR Researcher) RETURN p; is invalid syntax: label lists don’t accept OR inside the parentheses.
   - None of the answers is false because a correct form exists.

2. Equivalence and examples:
   - MATCH (p:Engineer:Researcher) RETURN p; is equivalent to MATCH (p) WHERE p:Engineer AND p:Researcher RETURN p;
   - Example: Node X labeled [Engineer, Researcher] matches; Node Y labeled [Engineer] does not; Node Z labeled [Researcher] does not.

Why the correct answer is correct:
- The pattern (p:Engineer:Researcher) enforces both labels at the pattern-matching level, so only nodes that are BOTH Engineer AND Researcher are returned. This directly meets the question requirement.

Why other options are incorrect:
- Option with OR in pattern: invalid syntax.
- Option with WHERE ... OR: returns nodes with either label, not both.
- Option with comma in WHERE: invalid syntax (should use AND).
- "None of the answers": incorrect because a correct query is present.

Conclusion: The correct query is MATCH (p:Engineer:Researcher) RETURN p; which matches the provided answer.

Q 12: Which query returns only people who are BOTH Engineer AND Researcher?单项选择题

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