openGauss每日一练第15天 | 逻辑结构：表管理3

1.创建表和约束

--首先创建一张测试表。

[omm@ogdb1 ~]$ gsql -p 40000
gsql ((openGauss 3.1.0 build 4e931f9a) compiled at 2022-09-29 14:19:24 commit 0 last mr  )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.

omm=# create table test(id bigint,name varchar(50) not null,age  int default 20,primary key(id) );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "test_pkey" for table "test"
CREATE TABLE
omm=#

2.使用\d tableNmae命令查看表的定义、模式和所有者

--在gsql中，使用\d tableNmae命令查看表的定义。
omm=#  \d+ test;
                                 Table "public.test"
 Column |         Type          | Modifiers  | Storage  | Stats target | Description
--------+-----------------------+------------+----------+--------------+-------------
 id     | bigint                | not null   | plain    |              |
 name   | character varying(50) | not null   | extended |              |
 age    | integer               | default 20 | plain    |              |
Indexes:
    "test_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default
Has OIDs: no
Options: orientation=row, compression=no

omm=#



--在gsql中，使用\d tableNmae命令查看表的模式和所有者。

omm=# \dt+ test;
                                    List of relations
 Schema | Name | Type  | Owner |  Size   |             Storage              | Description
--------+------+-------+-------+---------+----------------------------------+-------------
 public | test | table | omm   | 0 bytes | {orientation=row,compression=no} |
(1 row)

3.查看某个模式下有哪些表

--查看public模式下的所有表名：
 omm=# SELECT table_name FROM information_schema.tables WHERE table_schema='public';
 table_name
------------
 customer_t
 t1
 tab141
 tab142
 tab143
 tab144
 tab145
 tab1461
 tab1462
 test
(10 rows)

4.查看一个表下有哪些约束

--查看约束名称、约束类型
omm=# select conname, connamespace, contype, conkey  from pg_constraint where conrelid in (  elect oid  from pg_class  where relname='test');
  conname  | connamespace | contype | conkey
-----------+--------------+---------+--------
 test_pkey |         2200 | p       | {1}
(1 row)

omm=#



--或者使用gsql的元命令\d tableName很方便地查看一个表上有哪些约束
omm=#  \d test
             Table "public.test"
 Column |         Type          | Modifiers
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "test_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

5.查看一个表属于数据库的哪个模式

omm=# \x
Expanded display is on.

omm=# SELECT * FROM information_schema.tables WHERE table_name='test';
-[ RECORD 1 ]----------------+-----------
table_catalog                | omm
table_schema                 | public
table_name                   | test
table_type                   | BASE TABLE
self_referencing_column_name |
reference_generation         |
user_defined_type_catalog    |
user_defined_type_schema     |
user_defined_type_name       |
is_insertable_into           | YES
is_typed                     | NO
commit_action                |

omm=#