Database Index - Ordered Index

Ordered indexes / What is an ordered index? / Types of ordered index

Ordered indices

An index that is sorted and stored on its search key value is called as ordered index. For example, if you consider any book’s last page indexes, you would see that they are ordered on the topics. It makes us easy to visit the content related to the topic by searching in alphabetical order.

The ordering or sorting in ordered indices would mean two things;

1. Ordering of the index – that is, the search key values that are stored as part of the index file is ordered.
2. Ordering of the file in which the table or relation is stored – that is, the actual database records that are stored in a file in the same order as the index entries order.

The first one may be primary or secondary type indices (it depends on the ordering of the database file).

The second one is strictly a primary index.

A database file may have several indices depends on their requirements. These indices can be one of the following types;

• Primary index

• Secondary index

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