Posted by Erland Sommarskog on 06/09/06 22:13

ZeldorBlat (zeldorblat@gmail.com) writes:
> No, it won't. If you had a list of people on a piece of paper, sorted
> by last name and then by first name, explain how you would use that
> list to find everyone with a first name of "Joe" without looking
> through the entire list.

Say further that with each list there is a page number to references
where the persons appear in the book.

If all you want to know is the name of the persons, you can scan
the index, you don't have to read the whole book.

It's important to keep in mind that an index can be used in two
ways: Seek (look up data through the index tree) and Scan (read
the entire index from left to right): While the latter is far more
expensive, it can still be useful at times.



--
Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se

Books Online for SQL Server 2005 at
http://www.microsoft.com/technet/prodtechnol/sql/2005/downloads/books.mspx
Books Online for SQL Server 2000 at
http://www.microsoft.com/sql/prodinfo/previousversions/books.mspx

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