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：

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' );

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

su - omm
gsql -r
CREATE TABLESPACE enmtbs RELATIVE LOCATION 'tablespace/enmtbs1';
CREATE DATABASE musicdb WITH TABLESPACE = enmtbs;

omm=# CREATE TABLESPACE enmtbs RELATIVE LOCATION ‘tablespace/enmtbs1’;
CREATE TABLESPACE
omm=# CREATE DATABASE musicdb WITH TABLESPACE = enmtbs;
CREATE DATABASE
omm=#

2.查看数据库集簇中有哪些数据库

SELECT datname FROM pg_database;
或
\l

omm=# SELECT datname FROM pg_database;

datname

template1
omm
musicdb
template0
postgres
(5 rows)

omm=# \l

omm=# List of databases
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------±------±---------±--------±------±------------------
musicdb | omm | UTF8 | C | C |
omm | omm | UTF8 | C | C |
omm=#
omm=#
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)

omm=# SELECT datname FROM pg_database;
datname

template1
omm
musicdb
template0
postgres
(5 rows)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

select datname,dattablespace from pg_database where datname='musicdb';

select datname,dattablespace from pg_database where datname=‘musicdb’;
datname | dattablespace
---------±--------------
musicdb | 16390
(1 row)

4.查看数据库下有哪些模式

\dn+

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)
–或

SELECT catalog_name, schema_name, schema_owner FROM information_schema.schemata;

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：

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=# 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

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;

omm=# CREATE TABLESPACE app_ts RELATIVE LOCATION ‘tablespace/app_ts1’;
CREATE TABLESPACE
omm=#
omm=# ALTER DATABASE musicdb SET TABLESPACE app_ts;
ALTER DATABASE

–查看是否更改完成表空间

select spcname 
from pg_tablespace 
where oid=( select dattablespace
           from pg_database
           where datname='musicdb' );

omm=# --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.重新命名数据库

ALTER DATABASE musicdb RENAME TO  musicdb1;

\l

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;

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

\l

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)

9.删除数据库

DROP DATABASE musicdb1;

omm=# DROP DATABASE musicdb1;
DROP DATABASE