openGauss每日一练打卡第15天 | openGauss表管理3

学习目标

学习查看表的相关信息

课程学习

1.测试环境准备

--首先创建一张测试表。
drop table if exists test;
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"
omm=# CREATE TABLE

2.在gsql中查看表的定义、模式和所有者

--在gsql中，使用\d tableNmae命令查看表的定义。

 \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
--在gsql中，使用\d tableNmae命令查看表的模式和所有者。

\dt+ test;
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 
------------
 test
(1 row)

4.查看一个表下有哪些约束

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

--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
 \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

1. 查看一个表属于数据库的哪个模式

\x 

SELECT * FROM information_schema.tables WHERE table_name='test';
omm=# -[ 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

课程作业

1.创建表和约束

create table zhao(
id bigint,
name varchar(50) not null,
age  int default 20,
primary key(id)
     );

2.使用\d tableNmae命令查看表的定义、模式和所有者

\d+ zhao
                                 Table "public.zhao"
 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:
    "zhao_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default
Has OIDs: no
Options: orientation=row, compression=no

3.查看某个模式下有哪些表

\d+ zhao
                                 Table "public.zhao"
 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:
    "zhao_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default
Has OIDs: no
Options: orientation=row, compression=no

4.查看一个表下有哪些约束

omm=# SELECT table_name FROM information_schema.tables WHERE table_schema='public';
omm=# table_name
------------
test
zhao
(2 rows)

5.查看一个表属于数据库的哪个模式

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