openGauss每日一练第7天 | 随堂笔记

学习openGauss数据库、用户和模式的关系和访问方式，理解模式是在数据库层面，用户是在实例层面
一个用户连接到数据库后，可以在这个数据库中创建多个模式。要访问这些模式，可以使用DatabaseName.SchemaName.TableName或者SchemaName.TableName，来访问某个模式下的一个表。
默认情况下访问public模式下的表，可以不用添加模式名前缀。
1.查看当前数据库下有哪些模式

omm@modb:~$ gsql -d musicdb -U user1 -p 5432 -W kunpeng@1234 -r
gsql ((openGauss 3.0.0 build 02c14696) compiled at 2022-04-01 18:12:00 commit 0 last mr  )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.

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)

2.然后为数据库musicdb创建4个模式，名称可以自定义

musicdb=> \h create schema
Command:     CREATE SCHEMA
Description: define a new schema
Syntax:
CREATE SCHEMA schema_name
    [ AUTHORIZATION user_name ] [WITH BLOCKCHAIN] [ schema_element [ ... ] ];

musicdb=> create schema schm1 authorization omm; 
CREATE SCHEMA
musicdb=> create schema schm2 authorization omm; 
CREATE SCHEMA
musicdb=> create schema schm3  authorization omm;
CREATE SCHEMA
musicdb=> create schema schm4  authorization omm; 
CREATE SCHEMA
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           | omm
 schm2           | omm
 schm3           | omm
 schm4           | omm
 snapshot        | omm
 sqladvisor      | omm
(14 rows)

musicdb=> SELECT catalog_name, schema_name, schema_owner
musicdb-> FROM information_schema.schemata;
 catalog_name |    schema_name     | schema_owner 
--------------+--------------------+--------------
 musicdb      | pg_toast           | omm
 musicdb      | cstore             | omm
 musicdb      | pkg_service        | omm
 musicdb      | dbe_perf           | omm
 musicdb      | snapshot           | omm
 musicdb      | blockchain         | omm
 musicdb      | pg_catalog         | omm
 musicdb      | public             | omm
 musicdb      | sqladvisor         | omm
 musicdb      | dbe_pldebugger     | omm
 musicdb      | dbe_pldeveloper    | omm
 musicdb      | information_schema | omm
 musicdb      | db4ai              | omm
 musicdb      | schm1              | omm
 musicdb      | schm2              | omm
 musicdb      | schm3              | omm
 musicdb      | schm4              | omm
(17 rows)

3.在数据库musicdb的不同的模式下创建同名的表

musicdb=> 
musicdb=> create table schm1.ttt(col varchar(100));
CREATE TABLE
musicdb=> create table schm2.ttt(col varchar(100));
CREATE TABLE
musicdb=> create table schm3.ttt(col varchar(100));
CREATE TABLE
musicdb=> create table schm4.ttt(col varchar(100));
musicdb=> CREATE TABLE

musicdb=> insert into schm1.ttt values('Hello! from schema schm1   11111');
INSERT 0 1
musicdb=> insert into schm2.ttt values('Hello! from schema schm2   22222');
INSERT 0 1
musicdb=> insert into schm3.ttt values('Hello! from schema schm3   33333');
INSERT 0 1
musicdb=> insert into schm4.ttt values('Hello! from schema schm4   44444');
INSERT 0 1

musicdb=>  select table_catalog, table_schema, table_name, table_type
musicdb-> from information_schema.tables
musicdb-> where table_schema not in ('pg_catalog', 'information_schema','dbe_perf');

 musicdb       | schm3           | ttt        | BASE TABLE
 musicdb       | schm2           | ttt        | BASE TABLE
 musicdb       | schm1           | ttt        | BASE TABLE
(7 rows)

musicdb=>  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           | ttt        | BASE TABLE

4.查看用户在数据库中搜索模式的顺序

musicdb=> show SEARCH_PATH;
musicdb=>   search_path   
----------------
 "$user",public
(1 row)


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;
               col                
----------------------------------
 Hello! from schema schm4   44444
(1 row)

5.实验理解：模式是在数据库层面，用户是在实例层面

omm@modb:~$ gsql -d musicdb -U user1 -p 5432 -W kunpeng@1234 -r
gsql ((openGauss 3.0.0 build 02c14696) compiled at 2022-04-01 18:12:00 commit 0 last mr  )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.

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

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           | omm
 schm2           | omm
 schm3           | omm
 schm4           | omm
 snapshot        | omm
 sqladvisor      | omm
(14 rows)

musicdb=> \q
omm@modb:~$ gsql -r
gsql ((openGauss 3.0.0 build 02c14696) compiled at 2022-04-01 18:12:00 commit 0 last mr  )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.

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

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)

omm=# \q