openGauss每日一练第11天 | 数据库管理

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。

1.创建表空间enmtbs和数据库musicdb

omm=# CREATE DATABASE musicdb WITH TABLESPACE = enmtbs;
CREATE DATABASE
omm=# SELECT datname FROM pg_database;
  datname  
-----------
 template1
 omm
 musicdb
 template0
 postgres
(5 rows)

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

 spcname 
---------
 enmtbs
(1 row)

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;

---------------+-----------------+------------+------------
 omm           | db4ai           | snapshot   | BASE TABLE
 omm           | dbe_pldeveloper | gs_errors  | BASE TABLE
 omm           | dbe_pldeveloper | gs_source  | BASE TABLE

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.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)

8.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

9.删除数据库

omm=# DROP DATABASE musicdb1;
DROP DATABASE