Which data constraint specifies that values in a column must come from a defined, specific set (that is, only allowed values are permitted)?

Difficulty: Easy

Correct Answer: A domain constraint

Explanation:


Introduction / Context:
Constraints enforce data quality by restricting what can be stored. Among them, domain constraints govern the permissible set of values at the attribute level.



Given Data / Assumptions:

  • We want to restrict a column to a particular allowed set (for example, status ∈ {'New', 'Open', 'Closed'}).
  • The constraint applies to the attribute's legal values.


Concept / Approach:
A domain constraint defines the set of valid values for an attribute. It can be implemented with a CHECK constraint, an enumerated type, or a reference table with a foreign key. The key idea is that only listed or allowable values can exist in that column.



Step-by-Step Solution:

Recognize the requirement: whitelist of legal values.Map that to domain-level enforcement.Select “domain constraint”.


Verification / Alternative check:
DBMS documentation often shows domain checks as CHECK (status IN (...)) or by referencing a domain table.



Why Other Options Are Wrong:
Range constraint: Restricts by numeric/temporal range, not a discrete set.
Intrarelation/Interrelation constraints: Describe constraints within or between tables generally; they do not specifically denote value-domain restrictions.



Common Pitfalls:
Hard-coding value lists across application tiers instead of centralizing in the database; forgetting to validate during updates as well as inserts.



Final Answer:
A domain constraint

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