Which of the following statements is false?

Question

BlackTom AI · Accepted Answer

Identifying (strong) relationships are used when an entity type cannot be uniquely identified by its own attributes and therefore borrows the primary key of an owner entity; the weak entity’s primary key is a combination that includes the owner (identifying) entity’s primary key.

1) Relevant concepts:
- Strong (regular) entity: has its own primary key and independent existence.
- Weak entity: has no complete key on its own; its primary key includes the primary key of an owner.
- Identifying (strong) relationship: shown with a double diamond; links a weak entity to its owner so the owner’s key is part of the weak entity’s key.
- Non-identifying (weak) relationship: a normal relationship that does not contribute the owner’s key to the other entity’s primary key.

2) Step-by-step evaluation of choices:
- Option 1: "Strong (identifying) relationship connects a weak entity with a strong entity." This matches the standard definition: a weak entity is identified by a relationship to a strong (owner) entity. So this is true.
- Option 2: "Strong (identifying) relationship connects a weak entity and another weak entity." Although less common, this can occur in chained identification: a weak entity A may be owned by weak entity B if B itself is identified via its own owner; B’s key (which includes its owner’s key) can be part of A’s key. Thus an identifying relationship between two weak entities is possible in extended ER designs. So this statement can be considered true in that context.
- Option 3: "Strong (identifying) relationship connects two strong entities." This is incorrect because both strong entities already have independent primary keys. An identifying relationship only makes sense when one side lacks its own key and must incorporate the other’s key; two independently keyed (strong) entities do not require identification. Therefore this statement is false.
- Option 4: "Weak (non-identifying) relationship connects two strong entities." Standard practice: relationships among strong entities are non-identifying (single-diamond), so this is true.

3) No calculations required.

4) Why the correct answer is correct: Option 3 contradicts the core purpose of an identifying relationship (to convey an owner’s key to identify a dependent). Two strong entities don’t need that mechanism, so the statement is false.

Final confirmation: the false statement is "Strong (identifying) relationship connects two strong entities," matching the provided answer.

Which of the following statements is false?单项选择题

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