openGauss每日一练第7天|openGauss中一个数据库中可以创建多个模式

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。

连接数据库
#第一次进入等待15秒
#数据库启动中...
su - omm
gsql -r

root@modb:~# su - omm
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.

1.查看当前数据库下有哪些模式

omm=# CREATE TABLESPACE music_tbs RELATIVE LOCATION 'tablespace/test_ts1';
CREATE TABLESPACE
omm=# CREATE DATABASE musicdb  WITH TABLESPACE = music_tbs;
CREATE DATABASE
omm=#  CREATE USER user1 IDENTIFIED BY 'kunpeng@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# ALTER USER user1 SYSADMIN;
ALTER ROLEomm=# \q
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，名称自定义

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

3.在数据库musicdb的不同的模式下创建同名的表

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));
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');
musicdb=> INSERT 0 1

musicdb=> insert into schm4.ttt values('Hello! from schema schm4   44444');
INSERT 0 1

musicdb=>  create or replace view my_tables as
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');
CREATE VIEW
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       | public          | my_tables  | VIEW
 musicdb       | schm4           | ttt        | BASE TABLE
 musicdb       | schm3           | ttt        | BASE TABLE
 musicdb       | schm2           | ttt        | BASE TABLE
 musicdb       | schm1           | ttt        | BASE TABLE
(8 rows)

4.访问musicdb数据库下不同模式的同名表

musicdb=> show SEARCH_PATH;
  search_path   
----------------
 "$user",public
(1 row)
musicdb=> select * from schm1.ttt;                    
               col                
----------------------------------
 Hello! from schema schm1   11111
 Hello! from schema schm1   11111
(2 rows)
musicdb=>  select * from schm2.ttt;               
musicdb=>                col                
----------------------------------
 Hello! from schema schm2   22222
(1 row)
musicdb=>  select * from schm3.ttt;         
musicdb=>                col                
----------------------------------
 Hello! from schema schm3   33333
(1 row)
musicdb=>  select * from schm4.ttt;
musicdb=>                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, Policyadmin, UseFT | {}
 user1     | Sysadmin                                                        
                                                 | {}

musicdb=> \dn

 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)

     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | ommmusicdb=> 

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