I recently discovered (sadly) that WebSQL is no longer being supported for HTML5 and that IndexedDB will be replacing it instead.
I\'m wondering if there is any way
I mention some suggestions for querying relationships in my answer to this question, which may be of interest:
Conceptual problems with IndexedDB (relationships etc.)
As to querying multiple fields at once, it doesn't look like there's a native way to do that in IndexedDB (I could be wrong; I'm still new to it), but you could certainly create a helper function that used a separate cursor for each field, and iterated over them to see which records met all the criteria.