openGauss 每日一练第7天

原创酷酷咖啡 2022-11-30

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openGauss 每日一练第7天

准备

切换用户，连接数据库
```
su - omm
gsql -r
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```

创建表空间和测试数据库

CREATE TABLESPACE music_tbs RELATIVE LOCATION 'tablespace/test_ts1';
CREATE DATABASE musicdb  WITH TABLESPACE = music_tbs;
--创建用户并赋予 sysadmin 权限
 CREATE USER user1 IDENTIFIED BY 'abcd@1234';
 ALTER USER user1 SYSADMIN;
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1.查看当前数据库下有哪些模式

-- 使用用户user1 登录到 musicdb 中
gsql -r -U user1 -W abcd@1234 -d musicdb
-- -U 指定用户； -W 指定密码；-d 指定数据库
musicdb=> \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 dbe_perf        | omm
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 pkg_service     | omm
 public          | omm
 snapshot        | omm
 sqladvisor      | omm
(10 rows)
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2.然后为数据库musicdb创建4个模式，名称自定义

--  分别创建 schm1、schm2、schm3、schm4 ，指定owner 为user1
musicdb=> create schema  schm1  AUTHORIZATION user1;
CREATE SCHEMA
musicdb=> create schema  schm2  AUTHORIZATION user1;
CREATE SCHEMA
musicdb=> create schema  schm3  AUTHORIZATION user1;
CREATE SCHEMA
musicdb=> create schema  schm4  AUTHORIZATION user1;
musicdb=> CREATE SCHEMA

-- 查询当前模式
musicdb=> \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 dbe_perf        | omm
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 pkg_service     | omm
 public          | omm
 schm1           | user1
 schm2           | user1
 schm3           | user1
 schm4           | user1
 snapshot        | omm
 sqladvisor      | omm
(14 rows)

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3.在数据库musicdb的不同的模式下创建同名的表

create table schm1.ttt(col varchar(100));
create table schm1.tttaaabbbllleee(col varchar(100));
create table schm2.ttt(col varchar(100));
create table schm2.tttaaabbbllleee(col varchar(100));
create table schm3.ttt(col varchar(100));
create table schm3.tttaaabbbllleee(col varchar(100));
create table schm4.ttt(col varchar(100));
create table schm4.tttaaabbbllleee(col varchar(100));
-- 为每个表插入数据
insert into schm1.ttt values('Hello! from schema schm1   11111');
insert into schm2.ttt values('Hello! from schema schm2   22222');
insert into schm3.ttt values('Hello! from schema schm3   33333');
insert into schm4.ttt values('Hello! from schema schm4   44444');


-- 查询schm1 下所有的表
\dt schm1.*
                           List of relations
 Schema |   Name    | Type  | Owner |             Storage              
--------+-----------+-------+-------+----------------------------------
 schm1  | ttt       | table | user1 | {orientation=row,compression=no}
 schm1  | tttaaabbbllleee | table | user1 | {orientation=row,compression=no}
(2 rows
 
-- 创建视图，musicdb 下所有的表的视图：

create or replace view my_tables as
select table_catalog, table_schema, table_name, table_type
from information_schema.tables
where table_schema not in ('pg_catalog', 'information_schema','dbe_perf');

 -- 查询数据库musicdb 下所有的表
 musicdb=> select * from my_tables ;
 table_catalog |  table_schema   |   table_name    | table_type 
---------------+-----------------+-----------------+------------
 musicdb       | db4ai           | snapshot        | BASE TABLE
 musicdb       | dbe_pldeveloper | gs_errors       | BASE TABLE
 musicdb       | dbe_pldeveloper | gs_source       | BASE TABLE
 musicdb       | schm4           | tttaaabbbllleee | BASE TABLE
 musicdb       | schm4           | ttt             | BASE TABLE
 musicdb       | schm3           | tttaaabbbllleee | BASE TABLE
 musicdb       | schm3           | ttt             | BASE TABLE
 musicdb       | schm2           | tttaaabbbllleee | BASE TABLE
 musicdb       | schm2           | ttt             | BASE TABLE
 musicdb       | schm1           | tttaaabbbllleee | BASE TABLE
 musicdb       | schm1           | ttt             | BASE TABLE
 musicdb       | public          | my_tables       | VIEW

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4.访问musicdb数据库下不同模式的同名表

-- 通过 schema.table 来访问不同模式下的同名表
musicdb=> select * from schm1.ttt;  
               col                
----------------------------------
 Hello! from schema schm1   11111
(1 row)

musicdb=> select * from schm2.ttt;  
               col                
----------------------------------
 Hello! from schema schm2   22222
(1 row)

musicdb=> select * from schm3.ttt;  
               col                
----------------------------------
 Hello! from schema schm3   33333
(1 row)

musicdb=> select * from schm4.ttt;  
musicdb=>                col                
----------------------------------
 Hello! from schema schm4   44444
(1 row)
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5.实验理解：模式是在数据库层面，用户是在实例层面

用户是实例层面的：无论处于哪个库，执行\du命令所看到的结果都是一样的，用户列表是数据库级别的

-- 进入musicdb 库，查看用户

musicdb=> \c musicdb

Password for user user1: 
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "musicdb" as user "user1".
musicdb=> \du
                                                              List of roles
 Role name |                                                    Attributes                                                   | Member of 
-----------+-----------------------------------------------------------------------------------------------------------------+-----------
 gaussdb   | Sysadmin                                                                                                        | {}
 omm       | Sysadmin, Create role, Create DB, Replication, Administer audit, Monitoradmin, Operatoradmin, Policyadmin, UseFT| {}
 user1     | Sysadmin                                                                                                        | {}

-- 进入 omm 库，查看用户
musicdb=> \c omm
Password for user user1: 
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "omm" as user "user1".

omm=> \du
                                                              List of roles
 Role name |                                                  Attributes                                                     | Member of 
-----------+-----------------------------------------------------------------------------------------------------------------+-----------
 gaussdb   | Sysadmin                                                                                                         | {}
 omm       | Sysadmin, Create role, Create DB, Replication, Administer audit, Monitoradmin, Operatoradmin, Policyadmin, UseFT | {}
 user1     | Sysadmin                                                                                                         | {}

-- 由此可以看出，无论在哪个库下，所看到的用户列表一样，因此用户是实例层面的
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模式是数据库层面的：相同用户user1 进入不同库下，只能看到当前库中的模式，因此模式schame是数据库层面的

-- 切换到 musicdb 库，查看 当前库中的schema
omm=> \c musicdb
Password for user user1: 
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "musicdb" as user "user1".
musicdb=> \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 dbe_perf        | omm
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 pkg_service     | omm
 public          | omm
 schm1           | user1
 schm2           | user1
 schm3           | user1
 schm4           | user1
 snapshot        | omm
 sqladvisor      | omm
(14 rows)

-- 切换到 omm 库，查看当前库中的 schame
musicdb=> \c omm
Password for user user1: 
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "omm" as user "user1".
omm=> \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 dbe_perf        | omm
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 pkg_service     | omm
 public          | omm
 snapshot        | omm
 sqladvisor      | omm
 user1           | user1
(11 rows)

-- 由此可以看出 在omm 库中看不到 我们在musicdb 中创建的 schm1、schm2、schm3、schm4 模式，因此 模式是属于数据库层面的
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