Yes - just write a simple or weighted reverse index. Its trivial in any relational database and works accross tables and can be weighted by key columns or object attributes.
Don't use native RDBMS or SQL like unless you want your site to be as unsearchable as the millions of others out there.
Which reminds me - perl.com, and many perl sites (including search.cpan and perldoc.com) still have sucky searches - who else is interested in getting together and trying to improve them?
I am planning to port my current searchable class to Class::DBI, which might help. I will probably look at a module to provide a similar functionality in a procedural way to non-OO code.