Multiple Checkbox Filtering

Hi all, I am trying to compile a list of multiple checkboxes that will provide a filtering option for users to narrow down search results.

I have all my data stored in mysql database and have developed different queries in which I wish to apply to each checkbox. I.e Price variations 0-500, 500-1000. I am not quite sure how to use checkboxes to retrieve these queries from the database and most of all combine them when more than one is selected to filter the results.

I think ajax can also be used to display the results without loading the page again but I have never done this before and am completely stuck.
I would appreciate a nudge in the right direction :-)

The link below shows exactly what I am trying to achieve...
dfs.co.uk/sofas/leather-sofas/