openGauss每日一练第3天 课程笔记和作业

数据库环境

openGauss:2.0.0 - 数据库实训平台

学习目标

学习openGauss创建数据库、修改数据库属性和删除数据库

学习笔记

• 查看当前服务中有哪几个数据库

omm=# \l
                              List of databases
   Name    | Owner | Encoding |   Collate   |    Ctype    | Access privileges 
-----------+-------+----------+-------------+-------------+-------------------
 music1    | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 omm       | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 postgres  | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 template0 | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/omm           +
           |       |          |             |             | omm=CTc/omm
 template1 | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/omm           +
           |       |          |             |             | omm=CTc/omm
(5 rows)

• 修改数据库的最大连接数

ALTER DATABASE music CONNECTION LIMIT= 10;

• 进入数据库music2

omm=# \c music2;
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "music2" as user "omm".

课后作业

1.分别创建名为tpcc1和tpcc2的数据库

create database tpcc1;
create database tpcc2;

2.将tpcc1数据库重命名为tpcc10

alter database tpcc1 rename to tpcc10;

3.分别使用\l和\l+两个元命令查看数据库信息

omm=# \l
                              List of databases
   Name    | Owner | Encoding |   Collate   |    Ctype    | Access privileges 
-----------+-------+----------+-------------+-------------+-------------------
 music2    | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 omm       | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 postgres  | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 template0 | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/omm           +
           |       |          |             |             | omm=CTc/omm
 template1 | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/omm           +
           |       |          |             |             | omm=CTc/omm
 tpcc10    | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 tpcc2     | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
(7 rows)

omm=# \l+
                                                               List of databases
   Name    | Owner | Encoding |   Collate   |    Ctype    | Access privileges | Size  | Tablespace |                Description                 
-----------+-------+----------+-------------+-------------+-------------------+-------+------------+--------------------------------------------
 tpcc10    | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 |                   | 10 MB | pg_default | 
 tpcc2     | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 |                   | 10 MB | pg_default | 
 music2    | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 |                   | 10 MB | pg_default | 
 omm       | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 |                   | 10 MB | pg_default | 
 postgres  | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 |                   | 10 MB | pg_default | default administrative connection database
 template0 | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/omm           +| 10 MB | pg_default | default template for new databases
           |       |          |             |             | omm=CTc/omm       |       |            | 
 template1 | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/omm           +| 10 MB | pg_default | unmodifiable empty database
           |       |          |             |             | omm=CTc/omm       |       |            | 
(7 rows)

4.在数据库tpcc2中创建customer表，字段自定义

tpcc2=# create table customer(customer_id integer);
CREATE TABLE

5.删除新创建的数据库

tpcc2=# \l
                              List of databases
   Name    | Owner | Encoding |   Collate   |    Ctype    | Access privileges 
-----------+-------+----------+-------------+-------------+-------------------
 music2    | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 omm       | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 postgres  | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 template0 | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/omm           +
           |       |          |             |             | omm=CTc/omm
 template1 | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/omm           +
           |       |          |             |             | omm=CTc/omm
 tpcc10    | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 tpcc2     | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
(7 rows)

tpcc2=# drop database tpcc2;
ERROR:  cannot drop the currently open database
tpcc2=# \c omm;
omm=# Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "omm" as user "omm".

omm=# drop database tpcc2;
DROP DATABASE
omm=# drop database tpcc10;
DROP DATABASE
omm=# drop database music2;
DROP DATABASE
omm=# \l
                              List of databases
   Name    | Owner | Encoding |   Collate   |    Ctype    | Access privileges 
-----------+-------+----------+-------------+-------------+-------------------
 omm       | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 postgres  | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 template0 | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/omm           +
           |       |          |             |             | omm=CTc/omm
 template1 | omm   | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/omm           +
omm=#            |       |          |             |             | omm=CTc/omm
(4 rows)

6.退出gsql程序

omm=# \q

学习资源

• openGauss SQL学习参考资料
• 每日一练：openGauss数据库在线实训课程
• openGauss每日一练 | 21期养成好习惯，提升技术能力！
• 墨天轮Markdown编辑器使用介绍
• 墨天轮数据库在线实训平台V1.0操作手册
• 墨天轮数据社区

欢迎各位同学一起来交流学习心得！