swa66 - 1:45 am on Feb 14, 2013 (gmt 0)
That's actually pretty inefficient as you use the cartesian product (it's a kind on implicit join you use by listing multiple tables) : it matches every row of every table with every row of all the other tables creating a MONSTER intermediate table; and then it runs your where clauses to thin it out.
Using inner joins, you essentially move parts of your where clause to the join and make a much smaller intermediate table.
INNER JOIN series ON products.prod_series = series.series_id
INNER JOIN manufacturers ON series.series_man = manufacturers.man_id
products.prod_image IS NOT NULL
is all you need
The AS stuff I showed above is just a shorthand notation not to have to write the full table names all the time.
Use "explain" on your selects to see what it does ... you might be surprised by the number of records you had going there.