What are Oracle Indexes? Just like we have index present in the textbooks to help us find the particular topic in the book, Oracle index behaves the same way.we have different types of indexes in oracle. Indexes are used to search the rows in the table quickly. If the index is not present the select query has to read the whole table and returns the rows. With Index, the rows can be retrieved quickly We should create Indexes when selecting a small percentage of rows from a table (less than 2-4%). If the % of rows returned is high then index scan will be slow. It also depends on the data distribution i.e clustering factor Indexes are logically and physically independent of the data in the associate table. Indexes are optional structures associated with tables and clusters. You can create indexes on one or more columns of a table to speed SQL statement execution on that table. Indexes are the primary means of reducing disk I/O w