Ciro Santilli @cirosantilli 35

sudo -u postgres createuser -s $(whoami)
createdb $(whoami)

sudo cat /etc/postgresql/12/main/pg_hba.conf

local   all             postgres                                peer

# TYPE  DATABASE        USER            ADDRESS                 METHOD

# "local" is for Unix domain socket connections only
local   all             all                                     peer

psql -c '\du'

                                    List of roles
  Role name  |                         Attributes                         | Member of 
-------------+------------------------------------------------------------+-----------
 ciro        | Superuser, Create role, Create DB                          | {}
 owning_user |                                                            | {}
 postgres    | Superuser, Create role, Create DB, Replication, Bypass RLS | {}

psql -c 'DROP USER username;'

createdb testdb0

help

\?

\h

\h SELECT

psql -c '\l'

    Name     |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges   
-------------+----------+----------+-------------+-------------+-----------------------
 ciro        | postgres | UTF8     | en_GB.UTF-8 | en_GB.UTF-8 |
 postgres    | postgres | UTF8     | en_GB.UTF-8 | en_GB.UTF-8 |
 template0   | postgres | UTF8     | en_GB.UTF-8 | en_GB.UTF-8 | =c/postgres          +
             |          |          |             |             | postgres=CTc/postgres
 template1   | postgres | UTF8     | en_GB.UTF-8 | en_GB.UTF-8 | =c/postgres          +
             |          |          |             |             | postgres=CTc/postgres
 testdb0     | postgres | UTF8     | en_GB.UTF-8 | en_GB.UTF-8 |
(6 rows)

psql -c 'DROP DATABASE "testdb0";'

psql

\c testdb0

psql testdb0 -c 'CREATE TABLE table0 (int0 INT, char0 CHAR(16));'

psql testdb0 -c '\dt'

        List of relations
 Schema |  Name  | Type  | Owner
--------+--------+-------+-------
 public | table0 | table | ciro
(1 row)

psql testdb0 -c '\d+ table0'

                                      Table "public.table0"
 Column |     Type      | Collation | Nullable | Default | Storage  | Stats target | Description 
--------+---------------+-----------+----------+---------+----------+--------------+-------------
 int0   | integer       |           |          |         | plain    |              | 
 char0  | character(16) |           |          |         | extended |              | 

psql testdb0 -c "INSERT INTO table0 (int0, char0) VALUES (2, 'two'), (3, 'three'), (5, 'five'), (7, 'seven');"
psql testdb0 -c 'SELECT * FROM table0;'

 int0 |      char0
------+------------------
    2 | two
    3 | three
    5 | five
    7 | seven
(4 rows)

psql testdb0 -c 'DROP TABLE table0;'