Does an entity’s identifier determine the “type” of relationship it has, or does the identifier simply provide uniqueness while relationship type is governed by business rules and cardinality?

Database Data Modeling with ER Model Difficulty: Easy
Choose an option
  • A
    Incorrect
  • B
    Correct
  • C
    True only for weak entities
  • D
    True only when using surrogate keys
  • E
    ——

Answer

Correct Answer: Incorrect

Explanation

Introduction / Context: An identifier uniquely distinguishes entity instances. It does not decide whether a relationship is 1:1, 1:N, or N:M. Relationship type depends on business semantics and constraints expressed as cardinality and optionality, not on how we uniquely label instances.

Given Data / Assumptions:

  • Identifiers exist to ensure each entity instance is uniquely referenceable.
  • Relationships reflect how instances of entities are associated in the domain.
  • Keys (surrogate or natural) are implementation choices for uniqueness.

Concept / Approach: Decide relationship types by analyzing rules (e.g., “each Order must belong to one Customer” implies 1 on the Order side to Customer). The identifier does not change that determination. Whether the Customer identifier is CustomerNumber or a surrogate CustomerID is irrelevant to cardinality.

Step-by-Step Solution: Gather business rules that dictate participation counts. Set cardinalities accordingly (max/min). Choose identifiers to uniquely tag instances; keep this separate from relationship analysis.

Verification / Alternative check: Switch a natural key to a surrogate key in a model; the relationship types do not change, confirming independence from identifiers.

Why Other Options Are Wrong: Claiming identifiers determine relationship type confuses uniqueness with association semantics. Weak-entity or surrogate-key scenarios still do not make identifiers dictate cardinality.

Common Pitfalls: Letting technical key choices drive conceptual modeling; mixing normalization/key strategy with relationship semantics.

Final Answer: Incorrect

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