学习目标
学习openGauss体系结构，使用多个用户访问同一个数据库

课程学习
创建user1、user2、user3用户，验证数据库musicdb可以被用户user1、user2、user3访问（分别在数据库中创建了一张表、插入数据、进行查询）。即一个数据库可以被多个用户访问。

课后作业

1.创建用户user1、user2、user3，授予user1、user2、user3数据库系统的SYSADMIN权限

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

omm=# ALTER USER user1 SYSADMIN;
ALTER ROLE
omm=# ALTER USER user2 SYSADMIN;
ALTER ROLE
omm=# ALTER USER user3 SYSADMIN;
ALTER ROLE
omm=# \du
                                                              List of roles
 Role name |                                                    Attributes                                         
           | Member of 
-----------+-------------------------------------------------------------------------------------------------------
-----------+-----------
 gaussdb   | Sysadmin                                                                                              
           | {}
 omm       | Sysadmin, Create role, Create DB, Replication, Administer audit, Monitoradmin, Operatoradmin, Policyad
min, UseFT | {}
 user1     | Sysadmin                                                                                              
           | {}
 user2     | Sysadmin                                                                                              
           | {}
 user3     | Sysadmin                                                                                              
           | {}

2.分别使用user1、user2、user3访问数据库musicdb2，创建各自的表，并插入数据。表名和数据如下：

–以用户user1的身份在数据库musicdb中创建表t1，并插入一条数据：

musicdb=> create table products1(product_id integer,product_name char(20),category char(30));
CREATE TABLE
musicdb=> insert into products1 values(1502,'olympus camera','electrncs');
INSERT 0 1
musicdb=> insert into products1 values(1601,'lamaze','toys');
INSERT 0 1
musicdb=> insert into products1 values(1700,'wait interface','Books');
INSERT 0 1
musicdb=> insert into products1 values(1666,'harry potter','toys');
INSERT 0 1
musicdb=> select * from products1;
 product_id |     product_name     |            category            
------------+----------------------+--------------------------------
       1502 | olympus camera       | electrncs                     
       1601 | lamaze               | toys                          
       1700 | wait interface       | Books                         
       1666 | harry potter         | toys                          
(4 rows)

–以用户user2的身份在数据库musicdb中创建表t2，并插入一条数据：

musicdb-> \c musicdb user2
Password for user user2: 
Non-SSL connection (SSL connection is recommended when requiring high-security)
musicdb=> create table products2(product_id integer,product_name char(20),category char(30));
CREATE TABLE
musicdb=> insert into products2 values(1502,'olympus camera','electrncs');
INSERT 0 1
musicdb=> insert into products2 values(1601,'lamaze','toys');
INSERT 0 1
musicdb=> insert into products2 values(1700,'wait interface','Books');
INSERT 0 1
musicdb=> insert into products2 values(1666,'harry potter','toys');
INSERT 0 1
musicdb=> select * from products2; 
 product_id |     product_name     |            category            
------------+----------------------+--------------------------------
       1502 | olympus camera       | electrncs                     
       1601 | lamaze               | toys                          
       1700 | wait interface       | Books                         
       1666 | harry potter         | toys                          
(4 rows)

–以用户user3的身份在数据库musicdb中创建表t3，并插入一条数据：

musicdb=>   \c musicdb user3
Password for user user3: 
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "musicdb" as user "user3".
musicdb=> create table products3(product_id integer,product_name char(20),category char(30));
CREATE TABLE
musicdb=> insert into products3 values(1502,'olympus camera','electrncs');
INSERT 0 1
musicdb=> insert into products3 values(1601,'lamaze','toys');
INSERT 0 1
musicdb=> insert into products3 values(1700,'wait interface','Books');
INSERT 0 1
musicdb=> insert into products3 values(1666,'harry potter','toys');
INSERT 0 1
musicdb=> select * from products3; 
       1700 | wait interface       | Books                         
       1666 | harry potter         | toys                          
(4 rows)

musicdb=>  product_id |     product_name     |            category            
------------+----------------------+--------------------------------
       1502 | olympus camera       | electrncs                     
       1601 | lamaze               | toys 

3.使用user1、user2、user3用户中的任何一个，查看当前数据库musicdb2有哪些表

musicdb=> \c musicdb user1 
Password for user user1: 
musicdb=> Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "musicdb" as user "user1".

musicdb=> \dt
                           List of relations
 Schema |   Name    | Type  | Owner |             Storage              
--------+-----------+-------+-------+----------------------------------
 public | products1 | table | user1 | {orientation=row,compression=no}
 public | products2 | table | user2 | {orientation=row,compression=no}
 public | products3 | table | user3 | {orientation=row,compression=no}
(3 rows)