openGuass每日一练第6天|学习心得体会

课程学习内容

软件版本 ：openGauss 3.0.0

当用户user1连接到数据库musicdb1上时，没法访问数据库musicdb2上的表。

数据库实操内容

测试环境准备

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=# 

–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;

CREATE TABLESPACE music_tbs RELATIVE LOCATION ‘tablespace/test_ts1’;

CREATE DATABASE musicdb WITH TABLESPACE = music_tbs;

CREATE DATABASE musicdb1 WITH TABLESPACE = music_tbs;

CREATE DATABASE musicdb2 WITH TABLESPACE = 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
omm=# 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
omm=# CREATE DATABASE musicdb1  WITH TABLESPACE = music_tbs;
CREATE DATABASE
omm=# CREATE DATABASE musicdb2  WITH TABLESPACE = music_tbs;
CREATE DATABASE
omm=# 

–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=# 

–授予user1数据库系统的SYSADMIN权限：

ALTER USER user1 SYSADMIN;

omm=# ALTER USER user1 SYSADMIN;
ALTER ROLE
omm=# 

–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(col1 char(20));

insert into t11 values(‘Hello openGauss! 11’);

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=>  create table t11(col1 char(20));
CREATE TABLE
musicdb1=>  insert into t11 values('Hello openGauss! 11');
INSERT 0 1
musicdb1=>  select * from t11;
(1 row)

musicdb1=>          col1         
----------------------
 Hello openGauss! 11 

musicdb1=> 

–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(col1 char(20));

insert into t21 values(‘Hello openGauss! 22’);

select * from 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=>  create table t21(col1 char(20));
CREATE TABLE
musicdb2=>  insert into t21 values('Hello openGauss! 22');
INSERT 0 1
musicdb2=>  select * from t21;
         col1         
----------------------
 Hello openGauss! 22 
(1 row)

musicdb2=> 

使用用户连接数据库并访问表

使用user1用户连接到数据库musicdb1，并访问数据库musicdb1下的表t11：可以使用DatabaseName.SchemaName.TableName来标识openGauss中的一个表。

–使用user1用户连接到数据库musicdb1，访问数据库musicdb1下的表t11

\c musicdb1 user1

select * from musicdb1.public.t11;

musicdb2=> \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;
         col1         
----------------------
 Hello openGauss! 11 
(1 row)

musicdb1=> 

测试访问其他数据库下的表

在这个连接中（使用数据库用户user1连接到数据库musicdb1），如果试图访问数据库musicdb2下的t21表会报错:

select * from musicdb2.public.t21;

ERROR: cross-database references are not implemented: “musicdb2.public.t21” LINE 1:

select * from musicdb2.public.t21;

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

使用用户访问数据库并查询其下的表

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:

–可以正常访问，数据库中的表是存在的。但不能跨库访问。

\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;
         col1         
----------------------
 Hello openGauss! 22 
(1 row)

musicdb2=> 

课后作业

创建用户user1，分别在数据库musicdb1、数据库musicdb2创建表t11,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=# 
omm=#  CREATE USER user1 IDENTIFIED BY 'kunpeng@1234';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# ALTER USER user1 SYSADMIN;
ALTER ROLE
omm=# \c musicdb1 
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "musicdb1" as user "omm".
musicdb1=>  create table t11(col1 char(20));
CREATE TABLE
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(20));
CREATE TABLE

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

musicdb2=> \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;
(1 row)

musicdb1=>          col1         
----------------------
 Hello openGauss! 11 
musicdb1=> 

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=> 

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=> select * from musicdb2.public.t21;
         col1         
----------------------
 Hello openGauss! 22 
(1 row)

musicdb2=> 

课程学习体会
  通过本次的实训操作，了解到创建数据库和表的操作，用户访问musicdb1数据库能够正常访问该数据库下的表数据，而不能访问musicdb2数据库的表数据，而用户登录上musicdb2数据库也一样。