打卡第七天，心得体会
一个用户连接到数据库后，可以在这个数据库中创建多个模式。模式是在数据库层面，用户是在实例层面。
要访问这些模式，可以使用DatabaseName.SchemaName.TableName或者SchemaName.TableName，来访问某个模式下的一个表。
默认情况下访问public模式下的表，可以不用添加模式名前缀。
通过CREATE USER创建的用户，默认具有LOGIN权限。
通过CREATE USER创建用户的同时，系统会在执行该命令的数据库中，为该用户创建一个同名的SCHEMA。
课程作业
1.查看当前数据库下有哪些模式
omm=# \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)omm=# SELECT catalog_name, schema_name, schema_owner
omm-# 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)
2.然后为数据库musicdb创建4个模式，名称自定义
omm=# create database musicdb;
CREATE DATABASE
omm=# CREATE USER user1 IDENTIFIED BY 'kunpeng@1234';
NOTICE: The encrypted password contains MD5 ciphertext, which is not secure.
CREATE ROLE
omm=# \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
user1 | user1
(11 rows)
omm=# ALTER USER user1 SYSADMIN;
omm@modb:~$ gsql -d musicdb -U user1 -p 5432 -W kunpeng@1234 -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.
musicdb=> create schema schm1 AUTHORIZATION user1;
musicdb=> CREATE SCHEMA
musicdb=> create schema schm2 AUTHORIZATION user1;
CREATE SCHEMA
musicdb=> create schema schm3 AUTHORIZATION user1;
CREATE SCHEMA
musicdb=>
musicdb=> create schema schm4 AUTHORIZATION user1;
CREATE SCHEMA3.在数据库musicdb的不同的模式下创建同名的表
omm@modb:~$ gsql -d musicdb -U user1 -p 5432 -W kunpeng@1234 -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.
musicdb=> SELECT current_schema();
musicdb=> current_schema
----------------
public
(1 row)
musicdb=> SET SEARCH_PATH TO schm1;
SET
musicdb=> create table ttt (clo varchar2(20));
CREATE TABLE
musicdb=> \dt ttt;
List of relations
Schema | Name | Type | Owner | Storage
--------+------+-------+-------+----------------------------------
schm1 | ttt | table | user1 | {orientation=row,compression=no}
(1 row)
musicdb=> create table schm2.ttt(col varchar(100));
CREATE TABLE
musicdb=> create table schm3.ttt(col varchar(100));
musicdb=> CREATE TABLE
musicdb=> create table schm4.ttt(col varchar(100));
CREATE TABLE
musicdb=>
musicdb=> \dt
List of relations
Schema | Name | Type | Owner | Storage
--------+------+-------+-------+----------------------------------
schm1 | ttt | table | user1 | {orientation=row,compression=no}
(1 row)
musicdb=> create or replace view my_tables 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');
CREATE VIEW
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
musicdb | schm1 | my_tables | VIEW
musicdb | schm4 | ttt | BASE TABLE
musicdb | schm3 | ttt | BASE TABLE
musicdb | schm2 | ttt | BASE TABLE
musicdb | schm1 | ttt | BASE TABLE
(8 rows)
4.访问musicdb数据库下不同模式的同名表
musicdb=> select * from schm1.ttt;
clo
-----
(0 rows)
musicdb=> select * from schm2.ttt;
col
-----
(0 rows)
musicdb=> select * from schm3.ttt;
col
-----
(0 rows)
musicdb=>
musicdb=> select * from schm4.ttt;
col
-----
(0 rows)5.实验理解：模式是在数据库层面，用户是在实例层面
omm@modb:~$ gsql -d musicdb -U user1 -p 5432 -W kunpeng@1234 -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.
musicdb=> \du
List of roles
Role name | Attributes
| Member of
-----------+-------------------------------------------------------------------------------------------------------------
-----+-----------
gaussdb | Sysadmin
| {}
omm | Sysadmin, Create role, Create DB, Replication, Administer audit, Monitoradmin, Operatoradmin, Policyadmin, U
seFT | {}
user1 | Sysadmin
| {}
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
schm1 | user1
schm2 | user1
schm3 | user1
schm4 | user1
snapshot | omm
sqladvisor | omm
(14 rows)
musicdb=> \q
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=# \du
List of roles
Role name | Attributes
| Member of
-----------+-------------------------------------------------------------------------------------------------------------
-----+-----------
gaussdb | Sysadmin
| {}
omm | Sysadmin, Create role, Create DB, Replication, Administer audit, Monitoradmin, Operatoradmin, Policyadmin, U
seFT | {}
user1 | Sysadmin
| {}
omm=# \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
user1 | user1
(11 rows)
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