php faceted search

[casums]

i have table question(mysql with php) which contains question,category(multiple) and subcat(multiple) its belong. for simplification while saving each question i saved the category in comma separated as below\[code\]qid question catid subcat2 question1 2,3,4 5,7\[/code\]like this i have 1000 of question right now in DBwhile coming with faceted search i want to filter out for each category and its corresponding subcat like tree format below\[code\] cat1(5) subcat1(3) ......... cat2(24) ..........\[/code\]For this i just implemented in_array while searching for particular cat for each question in for each loop for that question table.The page getting slow now . along with text search also.is it really good idea or suggest me some right way .whether i wanna seperate table for category ?Thanxs,Gobi