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5天 | openGauss中一个用户可以访问多个数据库
学习目标
学习openGauss体系结构，使用一个用户访问多个数据库。
课程学习
数据库用户user1可以访问不同的数据库（musicdb1、musicdb2、musicdb3）。
实验中user1用户在数据库musicdb1中创建了表t11、在数据库musicdb2创建了表t21、在数据库musicdb3中创建了表t31，验证了这个结论。
1.测试环境准备：
1）–进入数据库omm
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.
omm=#
2）–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;
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=#
3）–创建表空间、测试数据库
CREATE TABLESPACE music_tbs RELATIVE LOCATION ‘tablespace/test_ts1’;
CREATE DATABASE musicdb1 WITH TABLESPACE = music_tbs;
CREATE DATABASE musicdb2 WITH TABLESPACE = music_tbs;
CREATE DATABASE musicdb3 WITH TABLESPACE = music_tbs;
omm=# CREATE TABLESPACE music_tbs RELATIVE LOCATION 'tablespace/test_ts1';
CREATE TABLESPACE
omm=# CREATE DATABASE musicdb1 WITH TABLESPACE = music_tbs;
CREATE DATABASE
omm=# CREATE DATABASE musicdb2 WITH TABLESPACE = music_tbs;
CREATE DATABASE
omm=# CREATE DATABASE musicdb3 WITH TABLESPACE = music_tbs;
CREATE DATABASE
omm=#
4）–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
omm=#
5）–授予user1数据库系统的SYSADMIN权限：
ALTER USER user1 SYSADMIN;
omm=# ALTER USER user1 SYSADMIN;
ALTER ROLE
omm=#
使用数据库用户user1登录到数据库musicdb1，创建一个表t11，并插入一条数据：
6）–用户user1登录到数据库musicdb1，创建表t11，并插入、查看数据
\c musicdb1 user1
omm=# \c musicdb1 user1
Password for user user1:
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "musicdb1" as user "user1".
musicdb1=>
7）–创建表t11，并插入、查看数据
create table t11(col1 char(20));
insert into t11 values(‘Hello openGauss! 11’);
select * from t11;
musicdb1=> create table t11(col1 char(20));
CREATE TABLE
musicdb1=> insert into t11 values('Hello openGauss! 11');
INSERT 0 1
musicdb1=> select * from t11;
col1
----------------------
Hello openGauss! 11
(1 row)
musicdb1=>
3.使用数据库用户user1登录到数据库musicdb2，创建一个表t21，并插入一条数据：
1）–用户user1登录到数据库musicdb2，创建表t21，并插入、查看数据
\c musicdb2 user1
musicdb1=> \c musicdb2 user1
Password for user user1:
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "musicdb2" as user "user1".
musicdb2=>
2）–创建表t21，并插入、查看数据
create table t21(col1 char(20));
insert into t21 values(‘Hello openGauss! 22’);
select * from t21;
musicdb2=> create table t21(col1 char(20));
musicdb2=> CREATE TABLE
musicdb2=>
musicdb2=> insert into t21 values('Hello openGauss! 22');
INSERT 0 1
musicdb2=> select * from t21;
(1 row)
musicdb2=> col1
----------------------
Hello openGauss! 22
musicdb2=>
4.使用数据库用户user1登录到数据库musicdb3，创建一个表t31，并插入一条数据：
1）–用户user1登录到数据库musicdb3
\c musicdb3 user1
musicdb2=> \c musicdb3 user1
Password for user user1:
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "musicdb3" as user "user1".
musicdb3=>
2）–创建表t31，并插入、查看数据
create table t31(col1 char(20));
insert into t31 values(‘Hello openGauss! 33’);
select * from t31;
musicdb3=> create table t31(col1 char(20));
CREATE TABLE
musicdb3=> insert into t31 values('Hello openGauss! 33');
INSERT 0 1
musicdb3=> select * from t31;
col1
----------------------
Hello openGauss! 33
(1 row)
musicdb3=>
课程总结
1.创建数据库musicdb10，创建用户user10，赋予sysadmin权限
2.用户user10访问数据库postgres，创建一个表并插入数据
3.用户user10访问数据库omm，创建一个表并插入数据
4.用户user10访问数据库musicdb10，创建一个表并插入数据
