[PHP] help with mysql query / logic

[Pablo Oliva]

I have 2 tables, one with job ad information, and a second one with the
locations that this ad applies to.
 
When a person queries the job ad table with their criteria, I would also
have to query the location table to see if the location that they chose
applies to this ad.  I am not sure how to construct the sql query
though, or if there is a better way to set this up.
 
Any suggestions will be appreciated.