[gentoo-alt] postgreql on prefix portage, doable?

Does anyone know, would it be practical to run an SQL server of some
variety in Prefix Portage? It would be for prototyping only.

Let me state at once that I have little experience with databases. I did
run mysql on native Gentoo for some time though, with no problems.

I see that there are things like postgresql and sqlite in the prefix tree.
Did anyone try them out?

And what is the difference between the postgresql-server and postgresql
packages? Different packagings of the same server? (I see now that there
is a Gentoo guide and it says `emerge postgresql' very early on..)

Rabbe Fogelholm