openGauss每日一练第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.创建模式、查看模式

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.
--进入数据库omm，创建表空间、测试数据库
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 musicdbb2;
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--执行下面的SQL语句，创建用户user1：
omm=# create user user1 identified by 'kunpeng@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
omm=# CREATE ROLE
--授予user1数据库系统的SYSADMIN权限：
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 -p5432 -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： sche1、 sche2、 sche3、 sche4

–用户user1在数据库musicdb中，创建了4个模式：
musicdb=> create schema sche1 authorization user1;
CREATE SCHEMA
musicdb=> create schema sche2 authorization user1;
CREATE SCHEMA
musicdb=> create schema sche3 authorization user1;
CREATE SCHEMA
musicdb=> create schema sche4 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
 sche1           | user1
 sche3           | user1
 sche4           | user1
 sche2           | user1
 snapshot        | omm
 sqladvisor      | omm
(14 rows)
–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：
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      | 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      | sche1              | user1
 musicdb      | sche2              | user1
 musicdb      | sche3              | user1
 musicdb      | sche4              | user1
(17 rows)

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 sche1.ttt(col varchar(100));
CREATE TABLE
musicdb=> create table sche2.ttt(col varchar(100));
CREATE TABLE
musicdb=> create table sche3.ttt(col varchar(100));
CREATE TABLE
musicdb=> create table sche4.ttt(col varchar(100));
 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 sche1.ttt values ('Hello! from schema sche1 111');
INSERT 0 1musicdb=> insert into sche2.ttt values ('Hello ! from schema sche2 222');
INSERT 0 1
musicdb=> insert into sche3.ttt values ('Hello! from schema sche3 333');
INSERT 0 1
musicdb=> insert into sche4.ttt values ('Hello! from schema sch4 444');
INSERT 0 1
--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=> 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');
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       | sche2           | ttt        | BASE TABLE
 musicdb       | sche4           | ttt        | BASE TABLE
 musicdb       | sche3           | ttt        | BASE TABLE
 musicdb       | sche1           | ttt        | BASE TABLE
(8 rows)

4.查看用户在数据库中搜索模式的顺序：

--查看默认的搜索模式的顺序
musicdb=> show search_path ;
(1 row)

musicdb=>   search_path   
----------------
 "$user",public
--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 sche1.ttt;
             col              
------------------------------
 Hello! from schema sche1 111
(1 row)
musicdb=> select * from sche2.ttt;
              col              
-------------------------------
 Hello ! from schema sche2 222
(1 row)
musicdb=> select * from sche3.ttt;
             col              
------------------------------
 Hello! from schema sche3 333
(1 row)

musicdb=> select * from sche4.ttt;
             col             
-----------------------------
 Hello! from schema sch4 444
(1 row)

5.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
musicdb=> gsql -d musicdb  -U user1 -p 5432 -W kunpeng@1234 -r
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
     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
 sche1           | user1
 sche3           | user1
 sche4           | user1
 sche2           | user1
 snapshot        | omm
 sqladvisor      | omm
(14 rows)

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, Policyadmin, 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

课程作业(使用上面的环境继续试验)

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
 sche1           | user1
 sche3           | user1
 sche4           | user1
 shce2           | user1
 snapshot        | omm
 sqladvisor      | omm
(14 rows)

2.然后为数据库musicdb创建4个模式，名称自定义

musicdb=> create schema xx1 authorization user1;
CREATE SCHEMA
musicdb=> create  schema  xx2 authorization  user1;
CREATE SCHEMA
musicdb=> create schema  xx3 authorization  user1;
CREATE SCHEMA
musicdb=> create schema xx4 authorization user1;
CREATE SCHEMA
musicdb=> \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 xx3             | user1
 xx4             | user1
(18 rows)

 dbe_perf        | omm
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 pkg_service     | omm
 public          | omm
 sche1           | user1
 sche3           | user1
 sche4           | user1
 shce2           | user1
 snapshot        | omm
 sqladvisor      | omm
 xx1             | user1
 xx2             | user1

3.在数据库musicdb的不同的模式下创建同名的表

musicdb=> create table xx1.tb(col varchar(100));
CREATE TABLE
musicdb=> create table xx2.tb(col varchar(100));
CREATE TABLE
musicdb=> create  table xx3.tb(col varchar(100));
CREATE TABLE
musicdb=> create  table xx4.tb(col varchar(100));
CREATE TABLE
musicdb=> insert into xx1.tb values ('Hello 111');
INSERT 0 1
musicdb=> insert into xx2.tb values ('Hello 222');
INSERT 0 1
musicdb=> insert into xx3.tb values ('Hello 333');
INSERT 0 1
musicdb=> insert into xx4.tb values ('Hello 444');
INSERT 0 1
musicdb=> 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');
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       | xx4             | tb         | BASE TABLE
 musicdb       | xx3             | tb         | BASE TABLE
 musicdb       | xx2             | tb         | BASE TABLE
 musicdb       | xx1             | tb         | BASE TABLE
 musicdb       | public          | my_tables  | VIEW
 musicdb       | shce2           | ttt        | BASE TABLE
 musicdb       | sche4           | ttt        | BASE TABLE
 musicdb       | sche3           | ttt        | BASE TABLE
 musicdb       | sche1           | ttt        | BASE TABLE
(12 rows)

4.访问musicdb数据库下不同模式的同名表

musicdb=> show search_path ;
musicdb=>   search_path   
----------------
 "$user",public
(1 row)
musicdb=> select  * from xx1.tb ;
    col    
-----------
 Hello 111
(1 row)

musicdb=> select  * from xx2.tb ;
    col    
-----------
 Hello 222
(1 row)

musicdb=> select  * from xx3.tb ;
    col    
-----------
 Hello 333
(1 row)

musicdb=> select  * from xx4.tb ;
    col    
-----------
 Hello 444
(1 row)

5.实验理解：模式是在数据库层面，用户是在实例层面

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
     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
 sche1           | user1
 sche3           | user1
 sche4           | user1
 shce2           | user1
 snapshot        | omm
 sqladvisor      | omm
 xx1             | user1
 xx2             | user1
 xx3             | user1
 xx4             | user1
(18 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, Policyadmin, 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
omm@modb:~$