openGauss每日一练第11天 | 学习心得体会

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。

1.创建表空间enmtbs和数据库musicdb

-- 连接openGuass数据库
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.
--清理测试数据
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 tablespace if exists enmtbs;
DROP TABLESPACE
omm=# NOTICE:  Tablespace "enmtbs" does not exist, skipping.
drop tablespace if exists app_ts;
DROP TABLESPACE
NOTICE:  Tablespace "app_ts" does not exist, skipping.
omm=# drop user if exists user1;
NOTICE:  role "user1" does not exist, skipping
DROP ROLE
-- 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=# \l
                         List of databases
   Name    | Owner | Encoding | Collate | Ctype | Access privileges 
-----------+-------+----------+---------+-------+-------------------
 musicdb   | 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 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=# \c musicdb omm
Non-SSL connection (SSL connection is recommended when requiring high-security)
You are now connected to database "musicdb" as user "omm".

musicdb=# \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 dbe_perf        | omm
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 pkg_service     | omm
 public          | omm
 snapshot        | omm
 sqladvisor      | omm
(10 rows)

5.查询当前连接的数据库下有哪些表：

musicdb=# with my_tables(table_catalog, table_schema, table_name, table_type) as
musicdb-#       (   select table_catalog, table_schema, table_name, table_type
musicdb(#           from information_schema.tables
musicdb(#          where table_schema not in ('pg_catalog', 'information_schema','dbe_perf')
musicdb(#        )
musicdb-#  select * from my_tables;
 table_catalog |  table_schema   | table_name | table_type 
---------------+-----------------+------------+------------
 musicdb       | db4ai           | snapshot   | BASE TABLE
 musicdb       | dbe_pldeveloper | gs_errors  | BASE TABLE
 musicdb       | dbe_pldeveloper | gs_source  | BASE TABLE
(3 rows)

6.更改数据库默认的表空间

musicdb=# CREATE TABLESPACE app_ts  RELATIVE LOCATION 'tablespace/app_ts1';
CREATE TABLESPACE
musicdb=# \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=# ALTER DATABASE musicdb  SET TABLESPACE app_ts;
ALTER DATABASE
--查看表空间是否更改完成
omm=# select spcname 
omm-# from pg_tablespace 
omm-# where oid=( select dattablespace
omm(# omm(#            from pg_database
           where datname='musicdb' );
 spcname 
---------
 app_ts
(1 row)

7.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  | 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)

8.修改数据库的默认用户

omm=# CREATE USER user1  IDENTIFIED BY 'test@123';
NOTICE:  The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# ALTER USER user1  SYSADMIN;
ALTER ROLE
omm=# ALTER DATABASE musicdb1 OWNER to user1;
ALTER DATABASE
omm=# \l
                         List of databases
   Name    | Owner | Encoding | Collate | Ctype | Access privileges 
-----------+-------+----------+---------+-------+-------------------
 musicdb1  | 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)

9.删除数据库

omm=# DROP DATABASE musicdb1;
DROP DATABASE
omm=# \l
                         List of databases
   Name    | Owner | Encoding | Collate | Ctype | Access privileges 
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
(4 rows)