Ripped from BOL, try using the BOL index next time


Using Clustered Indexes
A clustered index determines the storage order of data in a table. A
clustered index is analogous to a telephone directory, which arranges data
by last name. Because the clustered index dictates the physical storage
order of the data in the table, a table can contain only one clustered
index. However, the index can comprise multiple columns (a composite index),
like the way a telephone directory is organized by last name and first name.

A clustered index is particularly efficient on columns often searched for
ranges of values. Once the row with the first value is found using the
clustered index, rows with subsequent indexed values are guaranteed to be
physically adjacent. For example, if an application frequently executes a
query to retrieve records between a range of dates, a clustered index can
quickly locate the row containing the beginning date, and then retrieve all
adjacent rows in the table until the last date is reached. This can help
increase the performance of this type of query. Also, if there is a
column(s) which is used frequently to sort the data retrieved from a table,
it can be advantageous to cluster (physically sort) the table on that
column(s) to save the cost of a sort each time the column(s) is queried.


-----Original Message-----
From: nitai [mailto:nitai_12@h...]
Sent: 06 October 2000 00:18
To: sql language
Subject: [sql_language] Sql Indexing



I want to know what is the difference between clustured and nonclustured
indexing in sql. ligicaly how the index files created and how it is
funtioning logicaly when we will search a perticular value. what is
advatage and what is disadvantage both of these type of indexing.



nitai