From:	Aschwin Wesselius	Date:	Wed Apr 30 05:03:06 2008
Subject:	Re: Best practices for using MySQL index

Shelley wrote:
>> Don't index just all integer fields. Keep track of the cardinality of a
>> column. If you expect a field to have 100.000 records, but with only 500
>> distinct values it has no use to put an index on that column. A full record
>> search is quicker.
>>     
>
>    Hmmm... That's new. :)


Well, to give you a good measure: keep the cardinality between 30 to 
70-80 percent of your total records in a column. But sometimes your 
field is NULL or empty, so it really depends. You can't just put it into 
a standard configuration. And it also really depends on how many records 
a table contains etc.

Besides that, benchmarking your development environment (you do have one 
do you?) can gives you a good idea on how your hardware and setup performs.

Aschwin Wesselius