openGauss每日一练第 12 天| 学习心得体会

学习心得

本节课复习了shema的概念，并通过实践，巩固了schema的作用，强调了用户和schema的弱绑定关系。学习了不同级别如何修改默认的schema，并学习了怎么修改用户的schema

课后作业

1.创建一个名为testsm、testsm1的模式

omm=# create schema testsm authorization user1;
CREATE SCHEMA
omm=# create schema testsm1 authorization user1;
CREATE SCHEMA
omm=# 

2.创建一个用户john, 并将testsm的owner修改为john，且修改owner前后分别使用\dn+查看模式信息

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            |                                  | 
 john            | john  |                   |                                  | f
                 |       | =U/omm            |                                  | 
 snapshot        | omm   |                   | snapshot schema                  | f
 sqladvisor      | omm   | omm=UC/omm       +| sqladvisor schema                | f
                 |       | =U/omm            |                                  | 
 testsm          | user1 |                   |                                  | f
 user1           | user1 |                   |                                  | f
(14 rows)
--More-- pkg_service     | omm   |                   | pkg_service schema               | f
 public          | omm   | omm=UC/omm       +| standard public schema           | f
 testsm1         | user1 |                   |                                  | f

omm=# alter schema testsm owner to john; <---------------------------------修改schema的所属用户，这里体现了用户和schema的弱绑定关系

ALTER SCHEMA
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            |                                  | 
 john            | john  |                   |                                  | f
 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            |                                  | 
 testsm          | john  |                   |                                  | f
 testsm1         | user1 |                   |                                  | f
 user1           | user1 |                   |                                  | f

3.重命名testsm为testsm2

omm=# alter schema testsm rename to testsm2;
ALTER SCHEMA
omm=# \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 dbe_perf        | omm
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 john            | john
 pkg_service     | omm
 public          | omm
 snapshot        | omm
 sqladvisor      | omm
 testsm1         | user1
 testsm2         | john
 user1           | user1
(14 rows)

omm=# 

4.在模式testsm1中建表t1、插入记录和查询记录

omm=# create table testsm1.t1(i int);
CREATE TABLE
omm=# insert into testsm1.t1 values(1);
INSERT 0 1
omm=# select * from testsm1.t1;
 i 
---
 1
(1 row)

5.在会话级设置模式搜索顺序

omm=# set search_path to testsm1;
SET
omm=# show search_path;
 search_path 
-------------
 testsm1     <----------------会话级别，重新登陆失效
(1 row)

6.在数据库级设置模式搜索顺序

omm=# alter database omm set search_path to testsm2;
ALTER DATABASE
omm=# show search_path;
 search_path 
-------------
 testsm1         <-------------------数据库级别需要重新登陆生效
(1 row)

omm=# \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=# show search_path;
 search_path 
-------------
 testsm2
(1 row)

7.在用户级设置模式搜索顺序

omm=# alter user john set search_path to testsm1;  <-------------------修改
ALTER ROLE
omm=> \q
omm@modb:~$ gsql -d omm -U john -W john@123 -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=> show search_path;
 search_path 
-------------
 testsm1
(1 row)

omm=> \dn
     List of schemas
      Name       | Owner 
-----------------+-------
 blockchain      | omm
 cstore          | omm
 db4ai           | omm
 dbe_perf        | omm
 dbe_pldebugger  | omm
 dbe_pldeveloper | omm
 john            | john       <-------------------创建用户会默认创建对应的schema
 pkg_service     | omm
 public          | omm
 snapshot        | omm
 sqladvisor      | omm
 testsm1         | user1      <-------------------testsm1的默认用户仍然是user1
 testsm2         | john       <-------------------testsm2的默认用户仍然是john
 user1           | user1      <-------------------创建用户会默认创建对应的schema
(14 rows)
omm=> create table t2(i int);  <-------------------创建表不指定schema
CREATE TABLE
omm=> \dt t2;
omm=>                          List of relations
 Schema  | Name | Type  | Owner |             Storage              
---------+------+-------+-------+----------------------------------
 testsm1 | t2   | table | john  | {orientation=row,compression=no}   <-------------------默认为testsm1,而不是john
(1 row)