openGauss每日一练第11天 |openGauss逻辑结构：数据库管理

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：

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=# 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 ;
(5 rows)

omm=#   datname  
-----------
 template1
 omm
 musicdb
 template0
 postgres
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
–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 |         16389
(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=16389;
  oid  | spcname 
-------+---------
 16389 | 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 
-----------------+-------+-------------------+----------------------------------+----------------
 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            |                                  | 
 pkg_service     | omm   |                   | pkg_service schema               | f
 public          | omm   | omm=UC/omm       +| standard public schema           | f
                 |       | =U/omm            |                                  | 
 snapshot        | omm   |                   | snapshot schema                  | f
 sqladvisor      | omm   | omm=UC/omm       +| sqladvisor schema                | f
                 |       | =U/omm            |                                  | 
(10 rows)

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          | information_schema | omm
 omm          | db4ai              | omm
 omm          | sqladvisor         | omm
 omm          | dbe_pldebugger     | omm
 omm          | dbe_pldeveloper    | omm
(13 rows)

5.查询当前连接的数据库omm下有哪些表：

omm=# with my_tables 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-#  select * from my_tables;
omm=#  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)
--with as短语，也叫子查询部分，可以定义一个sql片段，该片段会被整个sql语句用到，可以使sql语句可读性更高，也可以在UNION ALL的不同部分，作为提供数据的部分。

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=# 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(#            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=# \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   | 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   | 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)

课程作业

1.创建表空间enmtbs2和数据库musicdb2

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=# create tablespace enmtbs2 relative location 'tablespace/enmtbs2';
CREATE TABLESPACE
omm=# create database musicdb2 with tablespace = enmtbs2;
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 spcname 
omm-# from pg_tablespace 
omm-# where oid=( select dattablespace
omm(#            from pg_database
omm(#            where datname='musicdb2' );
 spcname 
---------
 enmtbs2
(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
 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            |                                  | 
 pkg_service     | omm   |                   | pkg_service schema               | f
 public          | omm   | omm=UC/omm       +| standard public schema           | f
                 |       | =U/omm            |                                  | 
 snapshot        | omm   |                   | snapshot schema                  | f
 sqladvisor      | omm   | omm=UC/omm       +| sqladvisor schema                | f
                 |       | =U/omm            |                                  | 
(10 rows)

5.查询当前连接的数据库下有哪些表：

omm=# with my_tables as
omm-# omm(#       (   select table_catalog, table_schema, table_name, table_type
          from information_schema.tables
omm(#          where table_schema not in ('pg_catalog', 'information_schema','dbe_perf')
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=# alter database musicdb2 set tablespace app_ts ;
ALTER DATABASE
omm=# select spcname 
omm-# from pg_tablespace 
omm-# where oid=( select dattablespace
omm(#            from pg_database
omm(#            where datname='musicdb2' );
 spcname 
---------
 app_ts
(1 row)

7.重新命名数据库

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 musicdb2 owner to user1;
ALTER DATABASE
omm=# \l
                         List of databases
   Name    | Owner | Encoding | Collate | Ctype | Access privileges 
-----------+-------+----------+---------+-------+-------------------
omm=#  musicdb2  | 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.修改数据库的默认用户

omm=# alter database musicdb2 rename to xx1;
ALTER DATABASE
omm=# \l
                         List of databases
   Name    | Owner | Encoding | Collate | Ctype | Access privileges 
-----------+-------+----------+---------+-------+-------------------
 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
 xx1       | user1 | UTF8     | C       | C     | 
omm=# (5 rows)

9.删除数据库

omm=# drop database xx1 ;
DROP DATABASE