openGauss每日一练第6天|跨库查询测试

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

su - omm
gsql -r
--进入数据库omm，创建表空间、测试数据库
drop DATABASE  IF EXISTS  musicdb1;
drop DATABASE  IF EXISTS  musicdb2;
drop tablespace IF EXISTS music_tbs;
CREATE TABLESPACE music_tbs RELATIVE LOCATION 'tablespace/test_ts1';
CREATE DATABASE musicdb1  WITH TABLESPACE = music_tbs;
CREATE DATABASE musicdb2  WITH TABLESPACE = music_tbs;
--执行下面的SQL语句，创建用户user1：
CREATE USER user1 IDENTIFIED BY 'Mygstest@1234';
--授予user1数据库系统的SYSADMIN权限：
ALTER USER user1 SYSADMIN;
--用户user1登录到数据库musicdb1，创建表t11，并插入、查看数据
\c musicdb1 user1
create table t11(product_id INTEGER,product_name Char(20),category Char(30));
insert into t11 values(1511,'olympus camera','electrncs'),(1611,'lamaze','toys'),(1711,'wait interface','Books'),(1811,'harry potter','toys');
select * from t11;          
--用户user1登录到数据库musicdb2，创建表t21，并插入、查看数据
\c musicdb2 user1
create table t21(product_id INTEGER,product_name Char(20),category Char(30));
insert into t21 values(1522,'olympus camera','electrncs'),(1622,'lamaze','toys'),(1722,'wait interface','Books'),(1822,'harry potter','toys');
select * from t21;

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  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 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 musicdb1  WITH TABLESPACE = music_tbs;
CREATE DATABASE
omm=# CREATE DATABASE musicdb2  WITH TABLESPACE = music_tbs;
CREATE DATABASE
omm=# CREATE USER user1 IDENTIFIED BY 'Mygstest@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# ALTER USER user1 SYSADMIN;
ALTER ROLE
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=> create table t11(product_id INTEGER,product_name Char(20),category Char(30));
CREATE TABLE
musicdb1=> insert into t11 values(1511,'olympus camera','electrncs'),(1611,'lamaze','toys'),(1711,'wait interface','Books'),(1811,'harry potter','toys');
INSERT 0 4
musicdb1=> select * from t11;          
 product_id |     product_name     |            category            
------------+----------------------+--------------------------------
       1511 | olympus camera       | electrncs                     
       1611 | lamaze               | toys                          
       1711 | wait interface       | Books                         
       1811 | harry potter         | toys                          
(4 rows)


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(product_id INTEGER,product_name Char(20),category Char(30));
CREATE TABLE
musicdb2=> insert into t21 values(1522,'olympus camera','electrncs'),(1622,'lamaze','toys'),(1722,'wait interface','Books'),(1822,'harry potter','toys');
INSERT 0 4
musicdb2=> select * from t21;
 product_id |     product_name     |            category            
------------+----------------------+--------------------------------
       1522 | olympus camera       | electrncs                     
       1622 | lamaze               | toys                          
       1722 | wait interface       | Books                         
       1822 | harry potter         | toys                          
(4 rows)

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

\c musicdb1 user1
select * from t11;          

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=> select * from musicdb1.public.t11;
 product_id |     product_name     |            category            
------------+----------------------+--------------------------------
       1511 | olympus camera       | electrncs                     
       1611 | lamaze               | toys                          
       1711 | wait interface       | Books                         
       1811 | harry potter         | toys                          
(4 rows)

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)

--无法跨库访问musicdb2的表
\c musicdb1 user1
select * from musicdb1.public.t11;
select * from musicdb2.public.t21;

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=# \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=> select * from musicdb1.public.t11;
 product_id |     product_name     |            category            
------------+----------------------+--------------------------------
       1511 | olympus camera       | electrncs                     
       1611 | lamaze               | toys                          
       1711 | wait interface       | Books                         
       1811 | harry potter         | toys                          
(4 rows)

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。

--数据存在，但是不能跨库访问。
\c musicdb2 user1
 select * from musicdb2.public.t21;

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=>  select * from musicdb2.public.t21;
 product_id |     product_name     |            category            
------------+----------------------+--------------------------------
       1522 | olympus camera       | electrncs                     
       1622 | lamaze               | toys                          
       1722 | wait interface       | Books                         
       1822 | harry potter         | toys                          
(4 rows)

musicdb2=>