Multiple choice

What is the result if two NULL values are compared to each other?

  1. TRUE

  2. FALSE

  3. Undefined

  4. NULL
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The correct answer is D because in SQL, NULL is not a value but a marker for unknown/missing data. Any comparison operation involving NULL returns NULL (unknown), not TRUE or FALSE. Therefore, comparing two NULL values returns NULL, not TRUE, FALSE, or undefined. This is fundamental three-valued logic in SQL.

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