i have MySQL on my webserver but i need PostgreSQL for a application.
Can i have both MySQL and PostgreSQL on the same server ?
how do i install PostgreSQL?
server OS RH9 with WHM/Cpanel

Sure, you can run MySQL & postgresql at the same time.
Just go to postgresql.com , chose one of the mirrors to download from, and get the source distributions.
For example you can go to:
ftp://ftp9.us.postgresql.org/pub/mirrors/postgresql
grab the files you need.
[postgresql-base-7.1.tar.gz] is the only file you NEED.
but
[postgresql-opt-7.1.tar.gz] is good for use with lanuages, i.e PHP, Perl, etc..

Then read around and see the different ways you can install it, (it'll come with instructions, or just download those too.
You can just upload the "TarBall file" and then from the Linux Comand line uncompress it(I'm not exactly sure how to uncompress and Tarball file) Try: gzip postgresql-base-7.1.tar.gz

Hoped that helped.

Issuing the:
gzip postgresql-base-7.1.tar.gz

command, will give you this file;
postgresql-base-7.1.tar

Now issue:
tar -xvf postgresql-base-7.1.tar

and you'd start seeing the files untarred to their prespective directories.

There must be some readme/install/docs files that show you how to proceed.

G luck,
S.

I never had to do all of that to install postgres on my server. Have you tried /scripts/installpostgres yet?

Thanks for the help ... i think i wil go with the easy way and use the script

Yeah, forgot to mention thats the other way to do it depending on how you server is set up, I thought you tried that already, and needed another way.

i have MySQL installed and i wasn't sure if the two of em could be installed on the same server without messing it up
I have only been using MySQL so far on my servers

You likely won't need postgresql. I have it running but haven't found many scripts for it so haven't made use of it as of yet.