Hi,

> FB 1.5 Classic on Windows.
> Just wondering about the difference in speed in these 2 simple queries:
>
> select max(field1) from table1
>
> select max(field1) from table1 where field1 > 1000000
>
> The second one being a lot faster.
>
> The point is that this field has a unique ascending index, so if I do the
> simple phonebook analogy why is it faster to look at the last entry in the
> book or the last entry, but saying the name has to be > zaaa

Considering the phonebook:
You can only go to the last entry by going through them all -unless- you
know a way of skipping to the last entry and going backward, which is
what a DESCending index does.

So, given the phonebook, it's much faster to start at ZAAA and find
the "last entry" by going from ZAAA to ZZZZ then by starting at
AAAA and then going to ZZZZ.

Martijn Tonies
Database Workbench - tool for InterBase, Firebird, MySQL, NexusDB, Sybase
SQL Anywhere, Oracle & MS SQL Server
Upscene Productions
http://www.upscene.com
My thoughts:
http://blog.upscene.com/martijn/
Database development questions? Check the forum!
http://www.databasedevelopmentforum.com