What is an index, Database Management System

What is an Index?

An index is a small table having only two columns. The first column has a copy of the primary or candidate key of a table and the second column having a set of pointers holding the address of the disk block where that particular key value can be found.

The advantage of using index lies in the fact is that index makes search operation perform very fast. Suppose a table has a several rows of data, each row is 20 bytes wide. If you want to search for the record number 100, the management system must thoroughly read each and each row and after reading 99x20 = 1980 bytes it will search record number 100. If we have an index, the management system starts to search for record number 100 not from the table, but from the index. The index, having only two columns, might be just 4 bytes wide in each of its rows. After reading only 99x4 = 396 bytes of data from the index the management system search an entry for record number 100, reads the address of the disk block where record number 100 is stored and directly points at the record in the physical storage device. The result is a much faster access to the record (a speed benefit of 1980:396).

 

Posted Date: 7/26/2013 6:54:04 AM | Location : United States







Related Discussions:- What is an index, Assignment Help, Ask Question on What is an index, Get Answer, Expert's Help, What is an index Discussions

Write discussion on What is an index
Your posts are moderated
Related Questions
What is the meaning of Recovery? In deferred update methods, if a transaction fails before arriving its commit point, it will not have altered the database in any way, so UNDO


Critically evaluate the bulleted list of information-related items in this case study. How are each contradictory to the notion of being an information-literate knowledge worker?

a set of possible data value of an attribute is called??

What it creates while a primary key is combined with a foreign key? It creates Parent-Child relation ship between the tables that connect them while a primary key is combined w

Determine the Persistent object Persistent object can be stored in one of the following: Files Cheap, permanent, simple storage Low level (Write, Read) Ap

What is a records management consultation? Our organization is an authority for disseminating your specific requirements and giving you with a solution to effectively manage yo

Ask q“A database will be made to store information about patients in a hospital. On arrival, each patient’s personal details (name, address, and telephone number) are recorded wher

This report identifies and outlines my CIS 499 project named Traffic Data Management  Systems (TDMS) .   My goal is to design a replica of all traffic issues to be implemented i

Define two-phase locking protocol. Ans: Two-phase locking is significance in the context of ensuring that schedules are serializable. The two-phase locking protocol defines a p