openGauss每日一练第13天 |openGauss逻辑结构：表管理1

一、学习目标

学习openGauss表的创建、搜索路径和访问方法等

二、课程作业

1.创建一个表（默认，不指定模式），查看该表在那个模式下

--创建表空间enmtbs、数据库enmdb、用户user1，并授予用户user1 SYSADMIN权限：
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 enmdb WITH TABLESPACE = enmtbs;
CREATE DATABASE

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

--创建一个测试表pubtable，并插入一条数据：
enmdb=> show SEARCH_PATH;
  search_path   
----------------
 "$user",public
(1 row)

enmdb=> create table pubtable(col varchar(100));
CREATE TABLE
enmdb=> insert into pubtable values('Hello from pubtable!');
INSERT 0 1
enmdb=> select * from pubtable;
         col          
----------------------
 Hello from pubtable!
(1 row)

--查看pubtable表在那个模式下：
enmdb=> \dt
                          List of relations
 Schema |   Name   | Type  | Owner |             Storage              
--------+----------+-------+-------+----------------------------------
 public | pubtable | table | user1 | {orientation=row,compression=no}
(1 row)

enmdb=> select table_catalog,table_schema,table_name,table_type
enmdb-> from information_schema.tables 
enmdb-> where table_schema = 'public';
 table_catalog | table_schema | table_name | table_type 
---------------+--------------+------------+------------
 enmdb         | public       | pubtable   | BASE TABLE
(1 row)


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2.使用一个用户连接到enmdb数据库，测试该用户可以访问不同模式中的表

--以数据库用户user1的身份，连接到刚刚创建的数据库enmdb：
omm@modb:~$ gsql -d enmdb   -U user1   -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.

--执行下面的SQL语句，创建enmschm1、enmschm2模式
enmdb=> create schema enmschm1;
CREATE SCHEMA
enmdb=> create schema enmschm2;
CREATE SCHEMA

enmdb=> show SEARCH_PATH;
  search_path   
----------------
 "$user",public
(1 row)

enmdb=> SET SEARCH_PATH TO enmschm1;
SET

enmdb=> show SEARCH_PATH;
 search_path 
-------------
 enmschm1
(1 row)

enmdb=> select * from pubtable;
ERROR:  relation "pubtable" does not exist on gaussdb
LINE 1: select * from pubtable;
                      ^

enmdb=> select * from public.pubtable;
         col          
----------------------
 Hello from pubtable!
(1 row)

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3.在会话级设置模式搜索路径为:模式enmschm1,使用SchemaName.TableName的表标识方法访问表(创建表、插入数据和查询表中数据)

--执行下面的命令，在会话级重新设置模式搜索路径为模式enmschm1：
enmdb=> SET SEARCH_PATH TO enmschm1;
SET

--执行下面的命令，再次查看当前的模式搜索顺序：
enmdb=> show SEARCH_PATH;
 search_path 
-------------
 enmschm1
 
--在数据库enmdb的模式enmschm2中创建表schm2table：
enmdb=> create table enmschm2.schm2table(col varchar(100));
CREATE TABLE
enmdb=> insert into enmschm2.schm2table values('Hello from schm2table!');
INSERT 0 1
enmdb=> select * from enmschm2.schm2table;
          col           
------------------------
 Hello from schm2table!
(1 row)

--查看不同模式下的表
enmdb=> /dt

enmdb=> select table_catalog,table_schema,table_name,table_type
enmdb-> from information_schema.tables 
enmdb-> where table_schema = 'enmschm1';
 table_catalog | table_schema | table_name | table_type 
---------------+--------------+------------+------------
(0 rows)

enmdb=> select table_catalog,table_schema,table_name,table_type
enmdb-> from information_schema.tables 
enmdb-> where table_schema = 'enmschm2';
 table_catalog | table_schema | table_name | table_type 
---------------+--------------+------------+------------
 enmdb         | enmschm2     | schm2table | BASE TABLE
(1 row)


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