openGauss每日一练第11天-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：

su - omm
gsql -r
CREATE TABLESPACE enmtbs RELATIVE LOCATION 'tablespace/enmtbs1';
CREATE DATABASE musicdb WITH TABLESPACE = enmtbs;
2.查看数据库集簇中有哪些数据库
SELECT datname FROM pg_database;
或
\l
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：
select datname,dattablespace from pg_database where datname='musicdb';
–根据表空间对象的OID，来查看表空间的名字：
select oid,spcname from pg_tablespace where oid=16389;
–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：
select spcname 
from pg_tablespace 
where oid=( select dattablespace
           from pg_database
           where datname='musicdb' );
复制
4.查看数据库下有哪些模式
\dn+

 --或
SELECT catalog_name, schema_name, schema_owner FROM information_schema.schemata;
5.查询当前连接的数据库omm下有哪些表：
with my_tables(table_catalog, table_schema, table_name, table_type) as
      (   select table_catalog, table_schema, table_name, table_type
          from information_schema.tables
         where table_schema not in ('pg_catalog', 'information_schema','dbe_perf')
       )

 select * from my_tables;
6.更改数据库默认的表空间
CREATE TABLESPACE app_ts  RELATIVE LOCATION 'tablespace/app_ts1';

ALTER DATABASE musicdb  SET TABLESPACE app_ts;
--查看表空间是否更改完成
select spcname 
from pg_tablespace 
where oid=( select dattablespace
           from pg_database
           where datname='musicdb' );
7.修改数据库的默认用户
CREATE USER user1  IDENTIFIED BY 'user1@ustb2020';
ALTER USER user1  SYSADMIN;
ALTER DATABASE musicdb OWNER to user1;

\l
8.重新命名数据库
ALTER DATABASE musicdb RENAME TO  musicdb1;
\l
9.删除数据库
DROP DATABASE musicdb1;

课程作业
1.创建表空间enmtbs和数据库musicdb
```sql
omm=# create tablespace enmtbs RELATIVE LOCATION 'tablespace/enmtbs_1';
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
```sql
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)

omm=# select datname from pg_database;
  datname  
-----------
 template1
 omm
 musicdb
 template0
 postgres
(5 rows)


```
3.查看数据库默认的表空间信息
```sql
omm=# select datname,dattablespace from pg_database where datname='musicdb';
 datname | dattablespace 
---------+---------------
 musicdb |         16389
(1 row)

omm=# select oid,spcname from pg_tablespace where oid=16389;
  oid  | spcname 
-------+---------
 16389 | enmtbs
(1 row)


```
4.查看数据库下有哪些模式
```sql

omm=# \dn+    
                                         List of schemas
      Name       | Owner | Access privileges |           Description   
         | WithBlockChain 
-----------------+-------+-------------------+-------------------------
---------+----------------
 blockchain      | omm   |                   | blockchain schema       
         | f
 cstore          | omm   |                   | reserved schema for DELT
A 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          | sqladvisor         | omm
 omm          | dbe_pldebugger     | omm
 omm          | dbe_pldeveloper    | omm
 omm          | information_schema | omm
 omm          | db4ai              | omm
(13 rows)

```
5.查询当前连接的数据库下有哪些表：
```sql

omm=# with my_tables(table_catalog, table_schema, table_name, table_type) as
      (   select table_catalog, table_schema, table_name, table_type
          from information_schema.tables
         where table_schema not in ('pg_catalog', 'information_scheomm-# ma','dbe_perf')
       )

 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
```sql

omm=# create tablespace a_tbs RELATIVE LOCATION 'tablespace/atbs';
CREATE TABLESPACE
omm=# alter database musicdb set tablespace a_tbs;
ALTER DATABASE
omm=# select spcname 
from pg_tablespace 
where oid=( select dattablespace
           from pg_database
           where datname='musicdb' );

 spcname 
---------
 a_tbs
(1 row)

```
7.重新命名数据库
```sql


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
omm=# (5 rows)

```
8.修改数据库的默认用户
```sql

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=# 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
```sql

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)


```