Index STRUCTURES

There are three types of ordered single-levels of indexes.They are : 1)primary ,2) clustering,
and 3)secondary.Each index is specified on a field of the file.primary and clustering indexes are constructed on the physical ordering of a file , whereas secondary indexes are specified on non-ordering fields.the field for a primary index must also be a key of the file ,whereas it is a non-key field for a clustering index.a single-level index is an ordered file and is searched using an binary search.The nodes of these index structures are kept between half full and completely full by the insertion and deletion algorithms.