rdbms:create

Postgresql

CREATE database mydb;
CREATE user myuser with encrypted password 'mypass';
GRANT ALL PRIVILEGES ON DATABASE mydb TO myuser;
ALTER ROLE myuser WITH LOGIN;##

Mysql

CREATE USER 'user'@'%' IDENTIFIED WITH mysql_native_password BY 'password';
CREATE DATABASE mydb;
grant all privileges ON mydb.* TO 'myuser'@'%';