Check out example codes for "psql create user". It will help you in understanding the concepts better.

Code Example 1

# https://www.postgresql.org/docs/8.0/sql-createuser.html
CREATE USER <username> WITH PASSWORD '<password>' VALID UNTIL '<date here>';

Code Example 2

CREATE DATABASE yourdbname;CREATE USER youruser WITH ENCRYPTED PASSWORD 'yourpass';GRANT ALL PRIVILEGES ON DATABASE yourdbname TO youruser;

Code Example 3

psql=# grant all privileges on database <dbname> to <username>

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