Secondary indexes, Database Management System

Secondary Indexes

Let consider the student database and its clustering index and primary (only one will be applicable at a time). Now consider the state when the database is to be searched or accessed in the alphabetical order of names. Any search on a student name would need sequential data file search, therefore, is going to be very time consuming. Such a search on an average would need reading of half of the total number of blocks.

Therefore, we require secondary indices in database systems. A secondary index is files that have records having a secondary index field value which is not the ordering field of the data file, and a pointer to the block that have the data record. Please note that even if a data file can have only single primary index (as there can be only single ordering of a database file), it can have many secondary indices.

Secondary index can be described on an alternate key or non-key attributes. A secondary index that is described on the alternate key will be dense as secondary index on non-key attributes would need a bucket of pointers for one index entry. Let us define them in more detail with the help of Figures.

                        828_Secondary Indexes.png

Posted Date: 3/7/2013 6:31:01 AM | Location : United States







Related Discussions:- Secondary indexes, Assignment Help, Ask Question on Secondary indexes, Get Answer, Expert's Help, Secondary indexes Discussions

Write discussion on Secondary indexes
Your posts are moderated
Related Questions
Explain the term - Handling Boundary Condition These are some circumstances that to be handled in any system initialization and termination. Describes how system is bro


Suppose R is a relation with attributes A1, A2,..., An. As a function of n, tell how many superkeys R has, if: 1.1 The only key is A1. 1.2 The only key is A1 and A2. 1.3 The o


What is Relational DBMS This is our subject of study. A DBMS is relational if the data is organized into relations, that is, tables. In RDBMS, all data are kept in the well-kno

What Is Recovery?  During the life of a transaction, i.e., a after the start of a transaction but before the transaction commits, various changes may be made in a database state

what are information system hirarchy?

What are the physical characteristics of magnetic disks?   Ans: A magnetic disk is a circular plate or platter of plastic or metal that is coated with magnetizable material lik

What are the objectives of query processing?       Ans: The objectives of query processing is to transform a query written in a high level language into a accurate and efficien

Type of views :  Simple views and Difficult Views Feature Simple Views Complex Views Number of tables One