Database Reference
In-Depth Information
Working with Indexes
An index is a structure utilized for quick data retrieval operations. In the database
world, an index is associated with a table and used to eficiently locate data without
having to investigate every row in a database table. If a table does not have an index,
then a full table scan is needed to ind a record, which is very costly in terms of disk
I/O and CPU utilization. A full table scan is the process of sequentially reading
every record from disk, checking against search criteria, and building a result set.
In this chapter, you will learn the following topics:
• What is an index?
• How to create an index
• What are the different types of indexes?
• How to use different index methods
• Index problems
What is an index?
An index amends the performance of database operations at the cost of extra replicas
of data. As an index stores the extra copy of data for more speedy access, an index is
the routine way to amend the performance of the database. In a nutshell, an index is a
quick access path to a single row of a table in the database. A database index is similar
to a topic index where any speciic information can be located by looking at the index
page to avoid the full search of the topic, which is an exhaustive operation. Similarly, a
database index is created to minimize table traversal and maximize performance.
