AND Gate Filtering Sequence in MySQL

[aalnaif]

I was wondering about the filtering sequence that MySQL performs on AND gates. For example, consider the following query:

select *
from expl_table
where ColA > 30
and ColB < 15;

Does MySQL first select rows where ColA > 30, and then further filter the resultset for ColB < 15, or does it simply go through each row and select those rows that meet both criteria.

This is useful to know when indexing columns. Also, would anyone know of a good article or manual which explains this topic?

 

[r937]

article which explains mysql indexing:

http://hackmysql.com/case1

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