The clustering index is defined on the fields which are of type

Concept:

Indexing is a data structure technique to efficiently retrieve records from database files based on some attributes on which the indexing has been done. It is used to optimize the performance of database.

Explanation:

The index structure typically provides secondary access path i.e. alternate way of accessing the records without affecting the physical placement of records on disk.

There are several types of ordered indexes. A primary index is specified on the ordering key field of an ordered file of records. If ordering field is non key then it is known as clustering index. Non key and ordered means if numerous records in the file can have the same value for ordering field. Clustering index is also known as non-dense index.

Clustering index is an ordered file with two fields:

• First field is of same type as clustering of data file
• Second field is a block pointer.