Multiple choice technology databases

Which of following will require index.

  1. Not Null

  2. Check

  3. Unique key

  4. All of above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Unique key constraints require an index to enforce uniqueness efficiently. NOT NULL constraints and CHECK constraints do not require indexes - they're validation rules. Therefore, only unique keys (C) mandatorily require an index.

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