Some of the major indicationsof insufficient or incorrect indexing include:
A select statement takes too long.
A join between two or more tables takes an extremely long time.
Select operations perform well, but data modification processes perform poorly.
Point queries (for example, “where colvalue = 3”) perform well, but range queries (for example, “where colvalue > 3 and colvalue < 30”) perform poorly.
These underlying problems are described in the following sections.