Open terminal and invoke this command:
psql -U postgres
to create new database, invoke this command:
CREATE DATABASE mydatabase;
to create new user, invoke this command:
CREATE USER dbuser WITH PASSWORD 'mypassword';
then, you can set your desired user-related preference like this
ALTER ROLE dbuser SET client_encoding TO 'utf8';
ALTER ROLE dbuser SET default_transaction_isolation TO 'read committed';
ALTER ROLE dbuser SET timezone TO 'UTC';
to grant privileges, invoke this command:
GRANT ALL PRIVILEGES ON DATABASE mydatabase TO dbuser;
Quit from PostgreSQL console
OIDs basically give you a built-in, globally unique id for every row, contained in a system column (as opposed to a user-space column). That’s handy for tables where you don’t have a primary key, have duplicate rows, etc. For example, if you have a table with two rows identical rows, and you want to delete the oldest of the two, you could do that using the oid column.
In my experience, the feature is generally unused in most postgres-backed applications (probably in part because they’re non-standard), and their use is essentially deprecated:
In PostgreSQL 8.1 default_with_oids is off by default; in prior versions of PostgreSQL, it was on by default.
The use of OIDs in user tables is considered deprecated, so most installations should leave this variable disabled. Applications that require OIDs for a particular table should specify WITH OIDS when creating the table. This variable can be enabled for compatibility with old applications that do not follow this behavior.