search engine help

I have a page which displays a profile acording to a userid retrieved from a database. But as I'm writting a search engine now for my web, I realize that I want to be able to search by things such as location, interests, various things like that. and to be able to retrieve users not by exact username matching search term, but by maybe just a few words. how do I
a) retrieve items from the database that are simply close to search terms
and
b) use many url variables? seeing as how I use the userid to get the viewprofile page, I assumed that I need to jsut pass many userid's through the url, and then it will display them one after another. do I need to start making new variables? any help would be great. this forum has helped me so much!