Decision Support Systems
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Questions and Answers

What does an entity constraint ensure in a relational data model?

  • Every relation has a primary key and the primary key attributes cannot be NULL (correct)
  • Every attribute has a NOT NULL constraint
  • Every relation has a foreign key and the foreign key attributes cannot be NULL
  • Every attribute has a unique constraint

    • What does a domain constraint ensure?

  • Values of an attribute must be from different domains
  • Values of an attribute must be NULL
  • Values of an attribute must be unique
  • Values of an attribute must be from the same domain (correct)

    • What is the primary function of a primary key in a relational data model?

  • Uniquely identify tuples (correct)
  • Support entity constraints
  • Enforce domain constraints
  • Ensure referential integrity

    • What is the purpose of a referential constraint in a relational database?

    <p>Maintain referential integrity between tables (B)</p> Signup and view all the answers

    Why is it important for a primary key to have non-NULL attributes?

    <p>To ensure each tuple is uniquely identifiable (D)</p> Signup and view all the answers

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