12.2. Indexes
Indexes are used to significantly boost the performance of queries by reducing the amount of time needed to retrieve rows from a table. However, too many indexes on a table can be just as bad as not enough indexes.
Once you decide to create an index, you need to choose which type of index will work best. After you've created an index, you may need to change or drop it. Before dropping an index, you may want to monitor it to see how often it is used over a given time span. Finally, you can use data dictionary views to see the structure of the indexes in the database.
12.2.1. When to Create Indexes
In an environment where there are frequent insert, update, and delete operations on a table, it's wise to minimize the number of indexes ...
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