How to perform advanced searches on db

[eluser]Unknown[/eluser]
Well i read the thread you mentioned but my problem is not on the sql side.
My problem is how to build the query string that feeds the sql query.

I analized how codeigniter.com and expressionengine.com portals do their internal searches.
I think the solution would be to route the searches to a controller via post and then reload a view with the query string in the url.

Something like this:
Search for "foo"->route to controller "search"->load the view http://localhost/results/foo

Then you can build more complex query strings.

Don't think to implement third party apps anyway.