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      Question

      Which of the following statements accurately describes the characteristics of a primary key in a relational database?

      A A primary key can accept duplicate values as long as it is unique within the table. Correct Answer Incorrect Answer
      B A primary key is used to establish a link between two tables by referencing the foreign key in another table. Correct Answer Incorrect Answer
      C A primary key can be composed of multiple columns, and each combination of these columns must be unique across the table. Correct Answer Incorrect Answer
      D A primary key can be null if the table has other unique constraints. Correct Answer Incorrect Answer
      E A primary key is used solely for indexing purposes and does not enforce any uniqueness or integrity constraints. Correct Answer Incorrect Answer

      Solution

      A primary key is a critical concept in relational databases, ensuring that each record within a table can be uniquely identified. The primary key has the following key characteristics: • Uniqueness: Each value of a primary key must be unique across the entire table. No two rows can have the same primary key value. • Non-nullable: A primary key must always have a value; it cannot be null. This is essential for maintaining the integrity of the database as it ensures that every record can be uniquely identified.

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