openGauss每日一练第6天|学习openGauss体系结构

学习心得

学习openGauss体系结构，通过实验，了解用户一次只能连接到一个数据库，没法访问其他数据库的对象。

课后作业

1.创建用户user1，分别在数据库musicdb1、数据库musicdb2创建表t11,t21

omm=# CREATE TABLESPACE music_tbs RELATIVE LOCATION 'tablespace/test_ts1';
CREATE TABLESPACE
omm=# CREATE DATABASE musicdb1  WITH TABLESPACE = music_tbs;
omm=# CREATE DATABASE musicdb2  WITH TABLESPACE = music_tbs;CREATE DATABASE

CREATE DATABASE
omm=# CREATE USER user1 IDENTIFIED BY 'user@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# ALTER USER user1 SYSADMIN;
omm=# ALTER ROLE
omm=# 
\c musicdb1 user1
Password for user user1: 
musicdb1=> Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "musicdb1" as user "user1".

musicdb1=> create table t11(col1 char(50));
musicdb1=> CREATE TABLE
insert into t11 values('hello world 11');
INSERT 0 1
musicdb1=> select * from t11;
                        col1                        
----------------------------------------------------
 hello world 11                                    
(1 row)

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=> create table t21(col1 char(50));
CREATE TABLE
musicdb2=> insert into t21 values('hello world 22');
INSERT 0 1
select * from t21;
musicdb2=>                         col1                        
----------------------------------------------------
 hello world 22                                    
(1 row)

musicdb2=>

2.user1用户连接到数据库musicdb1，并访问数据库musicdb1下的表t11

musicdb1=> 
musicdb1=> select * from musicdb1.public.t11;
                        col1                        
----------------------------------------------------
 hello world 11                                    
(1 row)

musicdb1=> 

3.在这个连接中（使用数据库用户user1连接到数据库musicdb1）访问数据库musicdb2下的t21表(会报错)

musicdb1=> select * from musicdb2.public.t21;
ERROR:  cross-database references are not implemented: "musicdb2.public.t21"
LINE 1: select * from musicdb2.public.t21;
                      ^
musicdb1=> 

4.使用数据库用户user1连接到数据库musicdb2，访问数据库musicdb2下的t21表。

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=> 
musicdb2=> select * from musicdb2.public.t21;
musicdb2=>                         col1                        
----------------------------------------------------
 hello world 22                                    
(1 row)

musicdb2=>