SQL design approach for searching a table with an unlimited number of bit fields

Question

Consider searching a table that contains Apartment Rental Information: A client using the interface selects a number of criteria that are represented as bit fields in the D

Answer 1

I suggest you go with the second approach, known as Entity-attribute-value model. It's probably the only approach that will scale as you need.

You could also have two searches, the basic and the advanced. You keep the attributes for the basic search in one table, and all the advanced attributes in the other table. This way at least the basic search will remain rapid as the number of attributes will grow with time.