Well yeah, if you're moving all of your business logic into the database you're going to want DB-centered people.
EDIT: login -> logic
We don't move all logic into the database. Presentation logic, for example, is certainly not there. Also there are things like sales tax which cannot reasonably be put there.
The thing though is that one can always get a consultant to do sales tax logic. The big thing is if you know SQL and HTML the rest can come easily enough.
1) If you can, find someone with good, demonstrable SQL and PL/PGSQL experience.
2) If you can't find that, get someone who is competent in developing on Oracle.
"What?" comes the reply, "Don't they need to know Perl?"
I tell them that the use of Perl we have is getting more minimalistic and simpler, and that we are trying to make it so any competent developer can pick it up quickly.
The same would go if I was writing something similar in PHP. The issue is what sorts of fundamentally different technologies you can address, and the extent to which you feel comfortable working in both declarative, set-oriented worlds and object oriented approaches. The syntax on top of that is really less of an issue.