ahd=> \d user
                                    Table "public.user"
  Column  |         Type          | Collation | Nullable |             Default              
----------+-----------------------+-----------+----------+----------------------------------
 id       | integer               |           | not null | nextval('user_id_seq'::regclass)
 username | character varying(50) |           |          | 
 password | text                  |           |          | 
Indexes:
    "user_pkey" PRIMARY KEY, btree (id)
Referenced by:
    TABLE "post" CONSTRAINT "fk_user" FOREIGN KEY (user_id) REFERENCES "user"(id)

ahd=> SELECT * FROM "user";
 id |  username   |     password      
----+-------------+-------------------
  1 | ahd         | typewriter
  2 | random_dude | insecure_password
  9 | Idiot       | 1234567890
(3 rows)

ahd=> SELECT id FROM "user";
 id 
----
  1
  2
  9
(3 rows)

ahd=> SELECT id FROM "user" WHERE username = 'ahd' AND password = 'typewriter';
 id 
----
  1
(1 row)

ahd=> SELECT COUNT(id) FROM "user" WHERE username = 'ahd' AND password = 'typewriter';
 count 
-------
     1
(1 row)

ahd=> SELECT COUNT(id) FROM "user" WHERE username = 'ahd' AND password = 'typewridsafter';
 count 
-------
     0
(1 row)

ahd=>