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

1.查看当前数据库下有哪些模式

--创建表空间、测试数据库、用户及授权
omm=# CREATE TABLESPACE music_tbs RELATIVE LOCATION 'tablespace/music_ts1';
CREATE TABLESPACE
omm=# CREATE DATABASE musicdb  WITH TABLESPACE = music_tbs;
CREATE DATABASE
omm=# CREATE USER user1 IDENTIFIED BY 'kunpeng@2022';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# ALTER USER user1 SYSADMIN;
ALTER ROLE
--使用用户user1连接到数据库musicdb，首先查看当前数据库下有哪些模式；
omm=# \q
omm@modb:~$ gsql -d musicdb  -U user1 -p 5432 -W kunpeng@2022 -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.

--查看musicdb数据库下有哪些模式：
musicdb=> \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
musicdb=>  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

-–用户user1在数据库musicdb中，创建了4个模式：
  
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;
CREATE SCHEMA

–-查看musicdb数据库下有哪些模式：

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
 sqladvisor      | omm
(14 rows)

 schm3           | user1
 schm4           | user1
 snapshot        | omm

3.在数据库musicdb的不同的模式下创建同名的表

--在不同模式下，创建相同的表
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));
musicdb=> CREATE TABLE

--执行下面的SQL语句，往4个模式中的表ttt分别插入一条数据：
--在同一个数据库下，可以直接使用SchemaName.TableName来指定一个表，可以省略数据库名。
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

4.访问musicdb数据库下不同模式的同名表

--执行下面的SQL语句，查看musicdb数据库目前有哪些表
--创建视图：
musicdb->  select table_catalog, table_schema, table_name, table_type
musicdb-> from information_schema.tables
create or replace view my_tables as
musicdb-> where table_schema not in ('pg_catalog', 'information_schema','dbe_perf');
CREATE VIEW

--查看视图：
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)


--查看默认的搜索模式的顺序

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

--访问musicdb数据库下其他模式的表，需要指定模式名前缀：

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

--登录musicdb数据库，查看用户和模式
omm@modb:~$ gsql -d musicdb  -U user1 -p 5432 -W kunpeng@2022 -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
 omm       | Sysadmin, Create role, Create DB, Replication, Administer audit, Monitoradmin, Operatoradmin, Poli
cyadmin, UseFT | {}
 user1     | Sysadmin                                                                                          
               | {}

                                                              List of roles
 Role name |                                                    Attributes                                     
               | Member of 
-----------+---------------------------------------------------------------------------------------------------
---------------+-----------
 gaussdb   | Sysadmin                                                                                          
               | {}
musicdb=> \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
(14 rows)

 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
musicdb=> \q

--登录omm数据库，查看用户和模式

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
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 pkg_service     | omm
 public          | omm
 snapshot        | omm
 sqladvisor      | omm
 user1           | user1
(11 rows)

     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 dbe_perf        | omm
omm=# \q