Multiple choice

Which of the following statements is valid regarding index clusters?

  1. Index clusters can only be used for tables with low cardinality columns.

  2. Index clusters are generally well suited for tables that have many full table scans.

  3. Normal B-Tree indexes do not store null key values, whereas cluster indexes store null keys.

  4. A cluster index always takes up much more storage space than a normal index for the same set of key values.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In Oracle databases, standard B-Tree indexes exclude rows with NULL key values to save space, while cluster indexes include NULL entries in the index structure. This distinction is important because cluster indexes maintain the cluster key relationship even when values are null. Options A and B are incorrect because index clusters are typically used for high-cardinality columns and are not optimized for full table scans. Option D is incorrect because storage overhead depends on clustering factor, not the index type itself.

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