pg_locks ロックモード select (select relname from pg_class c where c.oid = l.relation) as relation (select distinct datname from pg_database d where d.oid = l.database) as database l.transaction l.pid l.mode l.granted from pg_locks l;

select カラム名 from テーブル名 limit 検索行数 offset 検索開始位置;

テスト問題出力等に使う select カラム名 from テーブル名 order by random() limit 検索行数;