Multiple choice technology databases

What are the situations when an index might not be picked up?

  1. Leading column in the index is not part of the search arguments

  2. Data types are not matching while doing a join

  3. Optimizer decides that table scan is better

  4. Index name is improper
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

Indexes are ignored if the leading column is missing from search arguments, or if mismatched data types force implicit conversions. The optimizer may also bypass an index for a table scan if selectivity is low. Index names do not affect optimizer decisions.

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