openGauss每日一练第 7 天 | openGauss 3.0.0数据库在线实训课程

作者：马顺华

从事运维管理工作多年，目前就职于某科技有限公司，熟悉运维自动化、OceanBase部署运维、MySQL 运维以及各种云平台技术和产品。并已获得OceanBase认证OBCA、OBCP证书。

第7天 | openGauss中一个数据库中可以创建多个模式

学习目标

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

课程学习

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.测试环境准备：

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

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.
omm=# 

2.创建模式、查看模式

1）–进入数据库omm，创建表空间、测试数据库

drop DATABASE IF EXISTS musicdb;
drop DATABASE IF EXISTS musicdb1;
drop DATABASE IF EXISTS musicdb2;
drop DATABASE IF EXISTS musicdb3;
drop tablespace IF EXISTS music_tbs;

CREATE TABLESPACE music_tbs RELATIVE LOCATION ‘tablespace/test_ts1’;
CREATE DATABASE musicdb WITH TABLESPACE = music_tbs;

omm=# drop DATABASE  IF EXISTS  musicdb;
NOTICE:  database "musicdb" does not exist, skipping
DROP DATABASE
omm=# drop DATABASE  IF EXISTS  musicdb1;
NOTICE:  database "musicdb1" does not exist, skipping
DROP DATABASE
omm=# drop DATABASE  IF EXISTS  musicdb2;
NOTICE:  database "musicdb2" does not exist, skipping
DROP DATABASE
omm=# drop DATABASE  IF EXISTS  musicdb3;
NOTICE:  database "musicdb3" does not exist, skipping
DROP DATABASE
omm=# drop tablespace IF EXISTS music_tbs;
NOTICE:  Tablespace "music_tbs" does not exist, skipping.
DROP TABLESPACE
omm=# CREATE TABLESPACE music_tbs RELATIVE LOCATION 'tablespace/test_ts1';
CREATE TABLESPACE
omm=# CREATE DATABASE musicdb  WITH TABLESPACE = music_tbs;
CREATE DATABASE
omm=# 

2）–执行下面的SQL语句，创建用户user1：

CREATE USER user1 IDENTIFIED BY ‘kunpeng@1234’;

omm=# CREATE USER user1 IDENTIFIED BY 'kunpeng@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE

3）–授予user1数据库系统的SYSADMIN权限：

ALTER USER user1 SYSADMIN;

omm=# ALTER USER user1 SYSADMIN;
ALTER ROLE

4）–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；

\q
gsql -d musicdb -U user1 -p 5432 -W kunpeng@1234 -r

omm=# \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

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)

musicdb=> 

3.然后为数据库musicdb创建4个模式： schm1、 schm2、 schm3、 schm4

1）–用户user1在数据库musicdb中，创建了4个模式：

create schema schm1 AUTHORIZATION user1;
create schema schm2 AUTHORIZATION user1;
create schema schm3 AUTHORIZATION user1;
create schema schm4 AUTHORIZATION 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;
CREATE SCHEMA
musicdb=> 

2）–查看musicdb数据库下有哪些模式：

\dn

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)

musicdb=> 

3）–除了可以用gsql的元命令\dn来查看数据库有哪些模式，还可以执行下面的SQL语句，查看某个数据库下有哪些模式：

SELECT catalog_name, schema_name, schema_owner FROM information_schema.schemata;

musicdb=> SELECT catalog_name, schema_name, schema_owner 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      | schm4              | user1
(17 rows)

 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              | user1
 musicdb      | schm2              | user1
 musicdb      | schm3              | user1
musicdb=> 

4.在数据库musicdb的不同的模式下创建同名的表：

1）–在不同模式下，创建相同的表

create table schm1.ttt(col varchar(100));
create table schm2.ttt(col varchar(100));
create table schm3.ttt(col varchar(100));
create table schm4.ttt(col varchar(100));

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=> 

2）–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。
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’);

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=> 

3）–执行下面的SQL语句，查看musicdb数据库目前有哪些表

–创建视图：

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’);

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=> 

4）----查看视图：

select * from my_tables;

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=>  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)

musicdb=> 

5.查看用户在数据库中搜索模式的顺序：

1）–查看默认的搜索模式的顺序

show SEARCH_PATH;

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

musicdb=> 

2）–访问musicdb数据库下其他模式的表，需要指定模式名前缀：

select * from schm1.ttt;

select * from schm2.ttt;

select * from schm3.ttt;

select * from schm4.ttt;

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)

musicdb=> 

6.模式是在数据库层面，用户是在实例层面

1）–登录musicdb数据库，查看用户和模式

gsql -d musicdb -U user1 -p 5432 -W kunpeng@1234 -r

musicdb-> \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.

\du

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
\q

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)

musicdb=> \q

2）–登录omm数据库，查看用户和模式

gsql -r

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

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                                                                                                         | 
{}

omm=# 

\dn
\q

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
omm@modb:~$ 

课程总结

1.查看当前数据库下有哪些模式

2.然后为数据库musicdb创建4个模式，名称自定义

3.在数据库musicdb的不同的模式下创建同名的表

4.访问musicdb数据库下不同模式的同名表

5.实验理解：模式是在数据库层面，用户是在实例层面