学习目标
数据库是数据库对象的容器，在数据库中，可以创建模式、表、索引等数据库对象。openGauss数据库管理包括：创建数据库、删除数据库、重新命名数据库、查看数据库的信息。
创建一个新的数据库。缺省情况下，新数据库将通过复制标准系统数据库template0来创建，且仅支持使用template0来创建。
课程学习
1.创建表空间enmtbs和数据库musicdb：
omm=# CREATE TABLESPACE enmtbs RELATIVE LOCATION 'tablespace/enmtbs1';
CREATE TABLESPACE
omm=# CREATE DATABASE musicdb WITH TABLESPACE = enmtbs;
CREATE DATABASE
2.查看数据库集簇中有哪些数据库
omm=# SELECT datname FROM pg_database;
datname
-----------
template1
omm
musicdb
template0
postgres
(5 rows)
omm=# omm=# \l
List of databases
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------+-------+----------+---------+-------+-------------------
musicdb | omm | UTF8 | C | C |
omm | omm | UTF8 | C | C |
omm=# postgres | omm | UTF8 | C | C |
template0 | omm | UTF8 | C | C | =c/omm +
| | | | | omm=CTc/omm
template1 | omm | UTF8 | C | C | =c/omm +
| | | | | omm=CTc/omm
(5 rows)
3.查看数据库默认的表空间信息
–首先执行下面的语句，查看musicdb数据库默认表空间的对象OID：
omm=# select datname,dattablespace from pg_database where datname='musicdb';
datname | dattablespace
---------+---------------
musicdb | 16405
(1 row)
–根据表空间对象的OID，来查看表空间的名字：
omm=# select oid,spcname from pg_tablespace where oid=16405;
oid | spcname
-------+---------
16405 | enmtbs
(1 row)
–可以将上面的两条语句合并成一条语句，来查询数据库musicdb默认表空间的名字
omm=# select spcname
omm-# from pg_tablespace
omm-# where oid=( select dattablespace
omm(# from pg_database
omm(# where datname='musicdb' );
spcname
---------
enmtbs
(1 row)
4.查看数据库下有哪些模式
omm=# \dn+
List of schemas
Name | Owner | Access privileges | Description | WithBlockChain
-----------------+-------+-------------------+----------------------------------+----------------
| | =U/omm | |
snapshot | omm | | snapshot schema | f
sqladvisor | omm | omm=UC/omm +| sqladvisor schema | f
blockchain | omm | | blockchain schema | f
cstore | omm | | reserved schema for DELTA tables | f
db4ai | omm | omm=UC/omm +| db4ai schema | f
| | =U/omm | |
dbe_perf | omm | | dbe_perf schema | f
dbe_pldebugger | omm | omm=UC/omm +| dbe_pldebugger schema | f
| | =U/omm | |
dbe_pldeveloper | omm | omm=UC/omm +| dbe_pldeveloper schema | f
| | =U/omm | |
jack | jack | | | f
pkg_service | omm | | pkg_service schema | f
public | omm | omm=UC/omm +| standard public schema | f
| | =U/omm | |
test | test | | | f
(12 rows)omm=#
omm=# --或
omm=# SELECT catalog_name, schema_name, schema_owner FROM information_schema.schemata;
catalog_name | schema_name | schema_owner
--------------+--------------------+--------------
omm | pg_toast | omm
omm | cstore | omm
omm | pkg_service | omm
omm | dbe_perf | omm
omm | snapshot | omm
omm | blockchain | omm
omm | pg_catalog | omm
omm | public | omm
omm | sqladvisor | omm
omm | dbe_pldebugger | omm
omm | dbe_pldeveloper | omm
omm | information_schema | omm
omm | db4ai | omm
omm | jack | jack
omm | test | test
5.查询当前连接的数据库omm下有哪些表：
omm=# with my_tables(table_catalog, table_schema, table_name, table_type) as
omm-# ( select table_catalog, table_schema, table_name, table_type
omm(# from information_schema.tables
omm(# where table_schema not in ('pg_catalog', 'information_schema','dbe_perf')
omm-# omm(# )
omm-#
select * from my_tables;
table_catalog | table_schema | table_name | table_type
---------------+-----------------+------------+------------
omm | db4ai | snapshot | BASE TABLE
omm | dbe_pldeveloper | gs_errors | BASE TABLE
omm | dbe_pldeveloper | gs_source | BASE TABLE
(3 rows)
6.更改数据库默认的表空间
omm=# CREATE TABLESPACE app_ts RELATIVE LOCATION 'tablespace/app_ts1';
CREATE TABLESPACE
omm=#
omm=# ALTER DATABASE musicdb SET TABLESPACE app_ts;
ALTER DATABASE
omm=# --查看表空间是否更改完成
omm=# select spcname
omm-# from pg_tablespace
omm-# omm(# where oid=( select dattablespace
from pg_database
omm(# where datname='musicdb' );
spcname
---------
app_ts
(1 row)
7.修改数据库的默认用户
omm=# CREATE USER user1 IDENTIFIED BY 'user1@ustb2020';
NOTICE: The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# ALTER USER user1 SYSADMIN;
ALTER ROLE
omm=# ALTER DATABASE musicdb OWNER to user1;
ALTER DATABASE
omm=#
omm=# \l
List of databases
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------+-------+----------+---------+-------+-------------------
musicdb | user1 | UTF8 | C | C |
omm | omm | UTF8 | C | C |
postgres | omm | UTF8 | C | C |
template0 | omm | UTF8 | C | C | =c/omm +
| | | | | omm=CTc/omm
template1 | omm | UTF8 | C | C | =c/omm +
| | | | | omm=CTc/omm
(5 rows)
8.重新命名数据库
omm=# ALTER DATABASE musicdb RENAME TO musicdb1;
ALTER DATABASE
omm=# \l
List of databases
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------+-------+----------+---------+-------+-------------------
musicdb1 | user1 | UTF8 | C | C |
omm=# omm | omm | UTF8 | C | C |
postgres | omm | UTF8 | C | C |
template0 | omm | UTF8 | C | C | =c/omm +
| | | | | omm=CTc/omm
template1 | omm | UTF8 | C | C | =c/omm +
| | | | | omm=CTc/omm
(5 rows)
9.删除数据库
omm=# DROP DATABASE musicdb1;
DROP DATABASE
课程作业
1.创建表空间enmtbs和数据库musicdb
omm=# CREATE TABLESPACE newtbs RELATIVE LOCATION 'tablespace/newtbs1';
CREATE TABLESPACE
omm=# CREATE DATABASE musicdb2 WITH TABLESPACE = newtbs;
CREATE DATABASE
2.查看数据库集簇中有哪些数据库
omm=# \l
List of databases
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------+-------+----------+---------+-------+-------------------
musicdb2 | omm | UTF8 | C | C |
omm | omm | UTF8 | C | C |
postgres | omm | UTF8 | C | C |
template0 | omm | UTF8 | C | C | =c/omm +
| | | | | omm=CTc/omm
template1 | omm | UTF8 | C | C | =c/omm +
| | | | | omm=CTc/omm
(5 rows)
3.查看数据库默认的表空间信息
omm=# select datname,dattablespace from pg_database where datname='musicdb2';
datname | dattablespace
----------+---------------
musicdb2 | 16412
(1 row)
4.查看数据库下有哪些模式
omm=# \dn+
List of schemas
Name | Owner | Access privileges | Description | WithBlockChain
-----------------+-------+-------------------+----------------------------------+----------------
blockchain | omm | | blockchain schema | f
cstore | omm | | reserved schema for DELTA tables | f
| | =U/omm | |
jack | jack | | | f
pkg_service | omm | | pkg_service schema | f
public | omm | omm=UC/omm +| standard public schema | f
db4ai | omm | omm=UC/omm +| db4ai schema | f
| | =U/omm | |
dbe_perf | omm | | dbe_perf schema | f
dbe_pldebugger | omm | omm=UC/omm +| dbe_pldebugger schema | f
| | =U/omm | |
dbe_pldeveloper | omm | omm=UC/omm +| dbe_pldeveloper schema | f
| | =U/omm | |
snapshot | omm | | snapshot schema | f
sqladvisor | omm | omm=UC/omm +| sqladvisor schema | f
| | =U/omm | |
test | test | | | f
user1 | user1 | | | f
(13 rows)
5.查询当前连接的数据库下有哪些表：
omm=# with my_tables(table_catalog, table_schema, table_name, table_type) as
omm-# ( select table_catalog, table_schema, table_name, table_type
omm(# from information_schema.tables
omm(# where table_schema not in ('pg_catalog', 'information_schema','dbe_perf')
omm-# omm(# )
omm-# select * from my_tables;
table_catalog | table_schema | table_name | table_type
---------------+-----------------+------------+------------
omm | db4ai | snapshot | BASE TABLE
omm | dbe_pldeveloper | gs_errors | BASE TABLE
omm | dbe_pldeveloper | gs_source | BASE TABLE
(3 rows)
6.更改数据库默认的表空间
omm=# CREATE TABLESPACE newapp_ts RELATIVE LOCATION 'tablespace/newapp_ts1';
CREATE TABLESPACE
omm=# ALTER DATABASE musicdb2 SET TABLESPACE newapp_ts;
ALTER DATABASE
omm=# select spcname
omm-# from pg_tablespace
omm-# where oid=( select dattablespace
omm(# from pg_database
omm(# where datname='musicdb2' );
spcname
-----------
newapp_ts
(1 row)
7.重新命名数据库
omm=# ALTER DATABASE musicdb2 RENAME TO musicdb3;
ALTER DATABASE
omm=# \l
List of databases
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------+-------+----------+---------+-------+-------------------
musicdb3 | omm | UTF8 | C | C |
omm | omm | UTF8 | C | C |
postgres | omm | UTF8 | C | C |
template0 | omm | UTF8 | C | C | =c/omm +
| | | | | omm=CTc/omm
omm=# template1 | omm | UTF8 | C | C | =c/omm +
| | | | | omm=CTc/omm
(5 rows)
8.修改数据库的默认用户
omm=# CREATE USER user2 IDENTIFIED BY 'user2@ustb2020';
NOTICE: The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# ALTER USER user2 SYSADMIN;
ALTER ROLE
omm=# ALTER DATABASE musicdb3 OWNER to user2;
ALTER DATABASE
omm=#
omm=# \l
List of databases
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------+-------+----------+---------+-------+-------------------
musicdb3 | user2 | UTF8 | C | C |
omm | omm | UTF8 | C | C |
postgres | omm | UTF8 | C | C |
template0 | omm | UTF8 | C | C | =c/omm +
| | | | | omm=CTc/omm
omm=# (5 rows)
template1 | omm | UTF8 | C | C | =c/omm +
| | | | | omm=CTc/omm
9.删除数据库
omm=# DROP DATABASE musicdb3;
DROP DATABASE
「喜欢这篇文章，您的关注和赞赏是给作者最好的鼓励」
关注作者
【版权声明】本文为墨天轮用户原创内容，转载时必须标注文章的来源（墨天轮），文章链接，文章作者等基本信息，否则作者和墨天轮有权追究责任。如果您发现墨天轮中有涉嫌抄袭或者侵权的内容，欢迎发送邮件至：contact@modb.pro进行举报，并提供相关证据，一经查实，墨天轮将立刻删除相关内容。
