Optimize select statement

Dolphin 6.0005

database query error when searching more than 10 miles from zip code

error:

Mysql error: The SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET SQL_MAX_JOIN_SIZE=# if the SELECT is okay Found error in file /home/dolphinsite/public_html/search_result.php at line 535

I have spoken to my hosting company and here is the response:

I would check your select statement to see if you can optimize it so I doesn't load so much data. We cannot change the size of MAX_JOIN_SIZE to a higher number. It will allow for queries that will make the whole server run slow. So optimization is the only route.

max_join size is set to 100,000,000

SQL big_selects is set to OFF in the server variables