openGauss每日一练第13天 | 学习心得体会

学习目标

学习openGauss表的创建、搜索路径和访问方法等

课程作业

测试环境搭建：
创建emtbs表空间，创建enmdb数据库属于emtbs表空间；创建用户user1，授权sysadmin；增加模式enmschm1和enmschm2。

root@modb:~# su - omm
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
omm=# \q
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.

enmdb=> create schema enmschm1;
enmdb=> CREATE SCHEMA
create schema enmschm2;
CREATE SCHEMA
enmdb=> 

1.创建一个表（默认，不指定模式），查看该表在那个模式下

omm=# create table testtable(col varchar(100));
CREATE TABLE

omm=# insert into testtable values('Hello from testtable!');
INSERT 0 1

omm=# \dt testtable
                           List of relations
 Schema |   Name    | Type  | Owner |             Storage              
--------+-----------+-------+-------+----------------------------------
 public | testtable | table | omm   | {orientation=row,compression=no}
(1 row)

omm=# 

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

前提：在enmdbs创建表testtable，新增Hello from testtable!数据。切换enmdbs1模式创建表testtable，新增Hello from testtable IN SCHEMA enmschm1!数据。

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

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

enmdb=> select * from testtable;
          col          
-----------------------
 Hello from testtable!
(1 row)

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=> create table testtable(col1  char(100));
CREATE TABLE
enmdb=> \dt
                            List of relations
  Schema  |   Name    | Type  | Owner |             Storage              
----------+-----------+-------+-------+----------------------------------
 enmschm1 | testtable | table | user1 | {orientation=row,compression=no}
(1 row)

enmdb=> insert into testtable values('Hello from testtable IN SCHEMA enmschm1!');
INSERT 0 1
enmdb=> select * from testtable;
                                                 col1                                           
      
------------------------------------------------------------------------------------------------
------
 Hello from testtable IN SCHEMA enmschm1!                                                       
     
(1 row)

结果查看：

enmdb=> select * from testtable;
                                                 col1                                           
      
------------------------------------------------------------------------------------------------
------
 Hello from testtable IN SCHEMA enmschm1!                                                       
     
(1 row)

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

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)

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

enmdb=> 
create table enmschm2.testtable(col1  char(100));
CREATE TABLE
enmdb=> create table enmschm2.testtable1(col1 char(100));
CREATE TABLE
enmdb=> create table enmschm2.testtable2(col1 char(100));
CREATE TABLE
enmdb=> insert into enmschm2.testtable values('Hello from testtable IN SCHEMA enmschm2!');
INSERT 0 1
enmdb=> select * from enmschm2.testtable;
                                                 col1                                           
      
------------------------------------------------------------------------------------------------
------
 Hello from testtable IN SCHEMA enmschm2!                                                       
     
(1 row)

enmdb=>