OS のユーザを切り替え。

su - postgres
最終ログイン: 2019/11/17 (日) 19:40:30 JST日時 pts/0

全てはここから。

psql -h [host_name] -p [port_no] -U [user_name] [db_name]

という書式でログイン。

psql -h localhost -p 5432 -U muchag testdb
psql (12.1)
"help"でヘルプを表示します。

で、下記のような、SQL 文入力待機状態になる。

postgres ユーザが postgres データベースへアクセスする場合のみ使える？

psql

\q

exit も有効。

psql --version
psql (PostgreSQL) 12.1

SELECT version();
                                                 version
---------------------------------------------------------------------------------------------------------
 PostgreSQL 12.1 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-39), 64-bit

\du
                                             ロール一覧
 ロール名 |                                   属性                                   | 所属グループ
----------+--------------------------------------------------------------------------+--------------
 postgres | スーパユーザ, ロール作成可, DB作成可, レプリケーション可, RLS のバイパス | {}

psql -l
                                        データベース一覧
   名前    |  所有者  | エンコーディング | 照合順序 | Ctype(変換演算子) |     アクセス権限
-----------+----------+------------------+----------+-------------------+-----------------------
 postgres  | postgres | UTF8             | C        | C                 |
 template0 | postgres | UTF8             | C        | C                 | =c/postgres          +
           |          |                  |          |                   | postgres=CTc/postgres
 template1 | postgres | UTF8             | C        | C                 | =c/postgres          +
           |          |                  |          |                   | postgres=CTc/postgres

\l
                                        データベース一覧
   名前    |  所有者  | エンコーディング | 照合順序 | Ctype(変換演算子) |     アクセス権限
-----------+----------+------------------+----------+-------------------+-----------------------
 postgres  | postgres | UTF8             | C        | C                 |
 template0 | postgres | UTF8             | C        | C                 | =c/postgres          +
           |          |                  |          |                   | postgres=CTc/postgres
 template1 | postgres | UTF8             | C        | C                 | =c/postgres          +
           |          |                  |          |                   | postgres=CTc/postgres

SHOW all;
SHOW [設定名];

psql --help

\?

\h
利用可能なヘルプ:
  ABORT                            ALTER PROCEDURE                  ALTER VIEW                       CREATE FOREIGN TABLE             CREATE TABLESPACE                DROP DATABASE                    DROP SCHEMA                      GRANT                            SELECT
  ALTER AGGREGATE                  ALTER PUBLICATION                ANALYZE                          CREATE FUNCTION                  CREATE TEXT SEARCH CONFIGURATION DROP DOMAIN                      DROP SEQUENCE                    IMPORT FOREIGN SCHEMA            SELECT INTO
  ALTER COLLATION                  ALTER ROLE                       BEGIN                            CREATE GROUP                     CREATE TEXT SEARCH DICTIONARY    DROP EVENT TRIGGER               DROP SERVER                      INSERT                           SET
  ALTER CONVERSION                 ALTER ROUTINE                    CALL                             CREATE INDEX                     CREATE TEXT SEARCH PARSER        DROP EXTENSION                   DROP STATISTICS                  LISTEN                           SET CONSTRAINTS
  ALTER DATABASE                   ALTER RULE                       CHECKPOINT                       CREATE LANGUAGE                  CREATE TEXT SEARCH TEMPLATE      DROP FOREIGN DATA WRAPPER        DROP SUBSCRIPTION                LOAD                             SET ROLE
  ALTER DEFAULT PRIVILEGES         ALTER SCHEMA                     CLOSE                            CREATE MATERIALIZED VIEW         CREATE TRANSFORM                 DROP FOREIGN TABLE               DROP TABLE                       LOCK                             SET SESSION AUTHORIZATION
  ALTER DOMAIN                     ALTER SEQUENCE                   CLUSTER                          CREATE OPERATOR                  CREATE TRIGGER                   DROP FUNCTION                    DROP TABLESPACE                  MOVE                             SET TRANSACTION
  ALTER EVENT TRIGGER              ALTER SERVER                     COMMENT                          CREATE OPERATOR CLASS            CREATE TYPE                      DROP GROUP                       DROP TEXT SEARCH CONFIGURATION   NOTIFY                           SHOW
  ALTER EXTENSION                  ALTER STATISTICS                 COMMIT                           CREATE OPERATOR FAMILY           CREATE USER                      DROP INDEX                       DROP TEXT SEARCH DICTIONARY      PREPARE                          START TRANSACTION
  ALTER FOREIGN DATA WRAPPER       ALTER SUBSCRIPTION               COMMIT PREPARED                  CREATE POLICY                    CREATE USER MAPPING              DROP LANGUAGE                    DROP TEXT SEARCH PARSER          PREPARE TRANSACTION              TABLE
  ALTER FOREIGN TABLE              ALTER SYSTEM                     COPY                             CREATE PROCEDURE                 CREATE VIEW                      DROP MATERIALIZED VIEW           DROP TEXT SEARCH TEMPLATE        REASSIGN OWNED                   TRUNCATE
  ALTER FUNCTION                   ALTER TABLE                      CREATE ACCESS METHOD             CREATE PUBLICATION               DEALLOCATE                       DROP OPERATOR                    DROP TRANSFORM                   REFRESH MATERIALIZED VIEW        UNLISTEN
  ALTER GROUP                      ALTER TABLESPACE                 CREATE AGGREGATE                 CREATE ROLE                      DECLARE                          DROP OPERATOR CLASS              DROP TRIGGER                     REINDEX                          UPDATE
  ALTER INDEX                      ALTER TEXT SEARCH CONFIGURATION  CREATE CAST                      CREATE RULE                      DELETE                           DROP OPERATOR FAMILY             DROP TYPE                        RELEASE SAVEPOINT                VACUUM
  ALTER LANGUAGE                   ALTER TEXT SEARCH DICTIONARY     CREATE COLLATION                 CREATE SCHEMA                    DISCARD                          DROP OWNED                       DROP USER                        RESET                            VALUES
  ALTER LARGE OBJECT               ALTER TEXT SEARCH PARSER         CREATE CONVERSION                CREATE SEQUENCE                  DO                               DROP POLICY                      DROP USER MAPPING                REVOKE                           WITH
  ALTER MATERIALIZED VIEW          ALTER TEXT SEARCH TEMPLATE       CREATE DATABASE                  CREATE SERVER                    DROP ACCESS METHOD               DROP PROCEDURE                   DROP VIEW                        ROLLBACK
  ALTER OPERATOR                   ALTER TRIGGER                    CREATE DOMAIN                    CREATE STATISTICS                DROP AGGREGATE                   DROP PUBLICATION                 END                              ROLLBACK PREPARED
  ALTER OPERATOR CLASS             ALTER TYPE                       CREATE EVENT TRIGGER             CREATE SUBSCRIPTION              DROP CAST                        DROP ROLE                        EXECUTE                          ROLLBACK TO SAVEPOINT
  ALTER OPERATOR FAMILY            ALTER USER                       CREATE EXTENSION                 CREATE TABLE                     DROP COLLATION                   DROP ROUTINE                     EXPLAIN                          SAVEPOINT
  ALTER POLICY                     ALTER USER MAPPING               CREATE FOREIGN DATA WRAPPER      CREATE TABLE AS                  DROP CONVERSION                  DROP RULE                        FETCH                            SECURITY LABEL

\h [SQL コマンド名] <- 詳細を見る

真面目に書くと、ログインできない。。。

psql -h localhost -p 5432 -U postgres
psql: エラー: サーバに接続できませんでした: FATAL:  Ident authentication failed for user "postgres"