Ordered Indices

Ordered Index

In an ordered index, keys are stored in the order that we want to parse them over.

Clustering Index

The index whose search key specifies the sequential order of the file is referred to as a clustering or a primary index. It is typically (but not necessarily) the primary key.

Secondary Index

An index whose search key is in an order different from the sequential order of the file is referred to as a non-clustering or secondary index.

Index-Sequential Access File (ISAM)

an ISAM is a sequential file ordered on a search key, with a clustering index on it. These are designed for applications that require both sequential and random access to records.