In many articles you will find the execution times of different
queries. Please do not interpret these results scientifically or as
official benchmarks. You will not even find the configuration of the
computer used for these experiments because it is rather unimportant.
What is important is that query A is running 2 times slower then
query B. On your computer, it could be different: 1.5 or even 3 times
slower. That is what I wanted to demonstrate.
The exact number is a different matter; it is much more difficult to
define. SQL server activity involves CPU, IO system (disk). There are
CPU-intensive and IO-intensive queries, and there are computers with
very slow hard drives like my notebook or server with SAN subsystems,
It would be extremely difficult to define an execution time for
different hardware configurations, depending on the CPU performance,
number of processors, hyperthreading, number of physical IO channels,
degree of parallelism and hundred other factors.
That is why these numbers are published ëas isí. They are not
scientific; they are just a result of a ëtest driveí of different ideas
As a source code is always provided for all tests, you will be able
to copy/paste scripts and reproduce tests in your environment. Just
donít forget to get rid of different artifacts like ëcache warmingí
(first execution takes much longer), you need to pre-allocate space on
your test database and set it to ëSimpleí recovery mode (otherwise SQL
server can stop during the experiment to add another chunk of space to
you data files) etc. So if you are running the same test 5 times and
the execution times are, say: 1023ms, 304ms, 300ms, 764ms, 304ms, then
the correct result is probably 300-304: the first one must be ignored
(see above), and 764ms was probably due to some kind of activity of
another process (even switching to another program during the
experiment can affect the result).