postgresql11 查看表结构和系统视图

postgres=# select * from pg_tables where tablename='t';
 schemaname | tablename | tableowner | tablespace | hasindexes | hasrules | hastriggers | rowsecurity 
------------+-----------+------------+------------+------------+----------+-------------+-------------
 public     | t         | postgres   |            | t          | f        | f           | f
(1 row)

postgres-# d t
                        Table "public.t"
 Column |         Type          | Collation | Nullable | Default 
--------+-----------------------+-----------+----------+---------
 id     | integer               |           | not null | 
 name   | character varying(20) |           |          | 
Indexes:
    "t_pkey" PRIMARY KEY, btree (id)

sql语句查看表结构
SELECT A
	.attnum,
	A.attname AS field,
	T.typname AS TYPE,
	A.attlen AS LENGTH,
	A.atttypmod AS lengthvar,
	A.attnotnull AS NOTNULL,
	b.description AS COMMENT 
FROM
	pg_class C,
	pg_attribute
	A LEFT OUTER JOIN pg_description b ON A.attrelid = b.objoid 
	AND A.attnum = b.objsubid,
	pg_type T 
WHERE
	C.relname = 't' 
	AND A.attnum > 0 
	AND A.attrelid = C.oid 
	AND A.atttypid = T.oid 
ORDER BY
	A.attnum;　

查看系统视图

postgres-# df pg_last*
                                                          List of functions
   Schema   |             Name              |     Result data type     |                  Argument data types                  | Type 
------------+-------------------------------+--------------------------+-------------------------------------------------------+------
 pg_catalog | pg_last_committed_xact        | record                   | OUT xid xid, OUT "timestamp" timestamp with time zone | func
 pg_catalog | pg_last_wal_receive_lsn       | pg_lsn                   |                                                       | func
 pg_catalog | pg_last_wal_replay_lsn        | pg_lsn                   |                                                       | func
 pg_catalog | pg_last_xact_replay_timestamp | timestamp with time zone |                                                       | func
(4 rows)

　　

系统视图 官方链接

https://www.postgresql.org/docs/current/catalogs.html