Major newbie - Part deux

Hi,

Thank you to Oliver for that help with my password questions. I have a
couple more questions:

1. Can I have entries in pg_hba.conf for specific databases and then end
with an entry for all so that I can protect certain databases one way and
all the rest another way? For example:

local xyz_db password
host xyz_db 127.0.0.1 255.255.255.255 password
local all trust
host all 127.0.0.1 255.255.255.255 trust

In theory I want to protect xyz_db with passwords, but all other databases
I will trust anyone who is local or is on a TCP/IP host.

2. What happens if I have an entry for a specific TCP/IP address will it
take that over the general address?

host all 127.0.0.1 255.255.255.255 trust
host all 192.168.90.0 255.255.255.255 password

Will this require a password from anyone on the 192.168.90.0 addresses, but
all other TCP/IP addresses will be trusted?

3. What is the difference in the following two lines?

host all 192.168.34.0 255.255.255.255 password
host all 192.168.34.0 255.255.255.0 password

(and please don't say that there is a 0 in one entry and a 255 in the other
:))

TIA,

David