Multiple choice technology databases

In which scenario would an index be most useful?

  1. The indexed column is declared as NOT NULL.

  2. The indexed columns are used in the FROM clause.

  3. The indexed columns are part of an expression.

  4. The indexed column contains a wide range of values.
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D Correct answer
Explanation

Indexes are most effective on columns with high cardinality - many distinct values relative to total rows. Low cardinality columns (like gender with only 2-3 values) see little benefit from indexing because each index entry points to many rows.

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