PostgreSQL is an advanced object-relational database management
system (ORDBMS) based on POSTGRES. With more than 15 years of
development history, it is quickly becoming the de facto
database for enterprise level open source solutions.

Before you can run postgresql you'll need to create the database;
please see README.SBo.

You need a "postgres" user and group prior to building postgresql.
Something like this will suffice for most systems:
  groupadd -g 209 postgres
  useradd -u 209 -g 209 -d /var/lib/pgsql postgres
Feel free to use a different uid and gid if desired, but 209 is
recommended to avoid conflicts with other stuff from SlackBuilds.org.