sql - Multi-dimensional search on a table -

i have following table stores preferences of users in system

userid | product   | brand     | city      | -------------------------------------------      | soap      | tide      | nyc       |      | cereal    | dont-care | nyc       | b      | dont-care | tide      | dont-care | c      | shampoo   | dont-care | dont-care | 

i search based on user provided search values. if 1 searches for

city: nyc, brand: tide 

the output should be:

       | soap      | tide      | nyc       |     b    | dont-care | tide      | dont-care | 

where if search for

brand: tide, product: soap 

the result should be:

       | soap      | tide      | nyc       | 

the current solution have, following query (where null represents 'don't care') going against mysql table:

select * user_preferences (product null or product = <user provided value>) , (brand null or brand = <user provided value>) , (city null or city = <user provided value>) 

though works expected, [and + (or)] combination makes me think not right way this. once dataset increases, query not perform well.

what efficient way of storing , retrieving such data? there no-sql type approaches can used make efficient?

update

after googling around figured approach have may safest bet. 1 factor still ambivalent approach adding 'searchable' attribute mean adding new column.

this blog eav anti-pattern provides reading material on such scheme. see how friend-feed uses mysql take on storing variable attributes in table.

you use ifnull() function.

it this:

select * user_preferences ifnull(product, <user provided value>) = <user provided value> , ifnull(brand, <user provided value>) = <user provided value> , ifnull(city, <user provided value>) = <user provided value>