how to create a new database in psql with username code example

Example 1: create db user postgres

sudo -u postgres psql
postgres=# create database mydb;
postgres=# create user myuser with encrypted password 'mypass';
postgres=# grant all privileges on database mydb to myuser;

Example 2: how to create new user and database postgresql in ubuntu

$ sudo -u postgres psqlpsql=# alter user <username> with encrypted password '<password>';