How to use Postgresql

$ sudo service postgresql status
● postgresql.service - PostgreSQL RDBMS
     Loaded: loaded (/lib/systemd/system/postgresql.service; enabled; vendor preset: enabled)
     Active: active (exited) since Sun 2025-02-02 10:21:38 JST; 56min ago
   Main PID: 12153 (code=exited, status=0/SUCCESS)
      Tasks: 0 (limit: 9312)
     Memory: 0B
     CGroup: /system.slice/postgresql.service

Feb 02 10:21:38 mozuku systemd[1]: Starting PostgreSQL RDBMS...
Feb 02 10:21:38 mozuku systemd[1]: Finished PostgreSQL RDBMS.

\q

\l

\d

cd /tmp
sudo -u postgres psql

$ cd /tmp
$ sudo -u postgres psql
psql (12.22 (Ubuntu 12.22-0ubuntu0.20.04.1))
Type "help" for help.

postgres=# 

CREATE USER myuser WITH PASSWORD 'mypassword';

CREATE DATABASE mydb OWNER myuser;

GRANT ALL PRIVILEGES ON DATABASE mydb TO myuser;

DROP DATABASE mydb;

DROP ROLE myuser;

psql -U myuser -d mydb -h localhost

CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    name TEXT NOT NULL,
    age INT
);

\d

mydb=> \d
             List of relations
 Schema |     Name     |   Type   | Owner  
--------+--------------+----------+--------
 public | users        | table    | myuser
 public | users_id_seq | sequence | myuser
(2 rows)

INSERT INTO users (name, age) VALUES ('Alice', 25), ('Bob', 30);

SELECT * FROM users;

UPDATE users SET age = 26 WHERE name = 'Alice';

DELETE FROM users WHERE name = 'Bob';