Multiple choice technology databases

Why one should not use NULL / NOT NULL operator on indexed columns?

  1. Using NULL / NOT NULL on indexed columns won’t use INDEX

  2. Using NULL / NOT NULL on indexed columns gives ERROR

  3. Using NULL / NOT NULL on indexed columns disables INDEX

  4. Using NULL / NOT NULL on indexed columns makes the INDEX unusable
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Explanation

When you use NULL or NOT NULL on an indexed column, the optimizer typically chooses a full table scan instead of using the index. This is because NULL values are not stored in most B-tree indexes (except bitmap indexes), making the index ineffective for NULL searches.

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