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首页 / openGauss每日一练第 16 天 | openGauss 3.0.0数据库在线实训课程

openGauss每日一练第 16 天 | openGauss 3.0.0数据库在线实训课程

原创 shunwah 2022-12-09
697

作者：马顺华

从事运维管理工作多年，目前就职于某科技有限公司，熟悉运维自动化、OceanBase部署运维、MySQL 运维以及各种云平台技术和产品。并已获得OceanBase认证OBCA、OBCP证书。

第16天 | openGauss逻辑结构：表管理4

学习目标

学习openGuass数据库中如何对表进行修改

课程学习

openGauss逻辑结构：表管理4

1.测试准备

–首先创建一张测试表。
drop table if exists test;
create table test(
id bigint,
name varchar(50) not null,
age int default 20,
primary key(id)
);

root@modb:~# 
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=# drop table if exists test;
DROP TABLE
NOTICE:  table "test" does not exist, skipping
omm=# create table test(
omm(#       id bigint,
omm(#       name varchar(50) not null,
omm(#       age  int default 20,
omm(#       primary key(id)
omm(#      );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "test_pkey" for table "test"
CREATE TABLE
omm=#

image.png

2.为表添加字段

–查看表test的信息
\d test

omm=# \d test
             Table "public.test"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "test_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

–为表test新增一列，列名为sex，数据类型为Boolean：
alter table test add column sex Boolean;

omm=# alter table test add column sex Boolean;
ALTER TABLE
omm=#

image.png
–执行下面gsql命令，查看表test的信息
\d test

omm=# 
omm=# \d test
             Table "public.test"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
 sex    | boolean               | 
Indexes:
    "test_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

3.删除表中的已有字段

–执行下面的SQL语句，删除刚刚添加的列sex：
alter table test drop column sex ;

omm=# alter table test drop column sex ;
ALTER TABLE
omm=#

image.png
–执行下面gsql命令，再次查看表test的信息
\d test

omm=# \d test
             Table "public.test"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "test_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

4.删除表的已有约束

–表test上有一个名叫test_pkey的PRIMARY KEY约束。执行下面的SQL语句，删除这个约束：
alter table test drop constraint test_pkey;

omm=# 
omm=# alter table test drop constraint test_pkey;
ALTER TABLE
omm=#

image.png

–执行下面的gsql命令，再次查看表test的信息：
\d test

omm=# \d test
             Table "public.test"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20

omm=#

image.png
–或直接查看约束是否被删除
select * from pg_constraint where conname like ‘test_pkey’;

omm=# select * from pg_constraint  where conname like 'test_pkey';
 conname | connamespace | contype | condeferrable | condeferred | convalidated | conrelid | contypid | conindid | confrelid | confupdtype | confdeltype | con
fmatchtype | conislocal | coninhcount | connoinherit | consoft | conopt | conkey | confkey | conpfeqop | conppeqop | conffeqop | conexclop | conbin | consrc 
| conincluding 
---------+--------------+---------+---------------+-------------+--------------+----------+----------+----------+-----------+-------------+-------------+----
-----------+------------+-------------+--------------+---------+--------+--------+---------+-----------+-----------+-----------+-----------+--------+--------
+--------------
(0 rows)

omm=#

image.png

5.为表添加约束

–执行下面的SQL命令，为表test添加刚刚删除的主键约束：
alter table test add constraint test_pkey primary key(id);

omm=# alter table test add constraint test_pkey primary key(id);
NOTICE:  ALTER TABLE / ADD PRIMARY KEY will create implicit index "test_pkey" for table "test"
ALTER TABLE
omm=#

image.png
–再次查看表test的信息：
select * from pg_constraint where conname like ‘test_pkey’;

\d test

omm=# 
omm=# select * from pg_constraint  where conname like 'test_pkey';
  conname  | connamespace | contype | condeferrable | condeferred | convalidated | conrelid | contypid | conindid | confrelid | confupdtype | confdeltype | c
onfmatchtype | conislocal | coninhcount | connoinherit | consoft | conopt | conkey | confkey | conpfeqop | conppeqop | conffeqop | conexclop | conbin | consr
c | conincluding 
-----------+--------------+---------+---------------+-------------+--------------+----------+----------+----------+-----------+-------------+-------------+--
-------------+------------+-------------+--------------+---------+--------+--------+---------+-----------+-----------+-----------+-----------+--------+------
--+--------------
 test_pkey |         2200 | p       | f             | f           | t            |    16389 |        0 |    16395 |         0 |             |             |  
             | t          |           0 | t            | f       | f      | {1}    |         |           |           |           |           |        |      
  | 
(1 row)

omm=# \d test
             Table "public.test"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "test_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

6.修改表字段的默认值

–执行下面的SQL语句，将age的默认值变更为25
alter table test alter column age set default 25;
\d test

omm=# alter table test alter column age set default 25;
ALTER TABLE
omm=# \d test
             Table "public.test"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 25
Indexes:
    "test_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

7.修改表字段的数据类型

alter table test ALTER COLUMN age TYPE bigint;
\d test

omm=# 
omm=# alter table test ALTER COLUMN age TYPE bigint;
ALTER TABLE
omm=# \d test
             Table "public.test"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | bigint                | default 25
Indexes:
    "test_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

8.修改表字段的名字

ALTER TABLE test RENAME COLUMN age TO stuage;
\d test

omm=# 
omm=# ALTER TABLE test RENAME COLUMN age TO stuage;
ALTER TABLE
omm=# \d test
             Table "public.test"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 stuage | bigint                | default 25
Indexes:
    "test_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

9.修改表的名字

–修改表的名字。执行下面的SQL语句，将表test的名字变更为mytest：
ALTER TABLE test RENAME TO mytest;
\d mytest

omm=# 
omm=# ALTER TABLE test RENAME TO mytest;
ALTER TABLE
omm=# \d mytest
            Table "public.mytest"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 stuage | bigint                | default 25
Indexes:
    "test_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

10.删除表

DROP TABLE mytest;

omm=# DROP TABLE mytest;
DROP TABLE
omm=#

image.png

课程作业

1.创建表，为表添加字段

2.删除表中的已有字段

3.删除表的已有约束、添加约束

4.修改表字段的默认值

5.修改表字段的数据类型

6.修改表字段的名字

7.修改表的名字

8.删除表

1.创建表，为表添加字段

root@modb:~# 
root@modb:~# 
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=# drop table if exists test666;
NOTICE:  table "test666" does not exist, skipping
DROP TABLE
omm=# create table test666(
omm(#       id bigint,
omm(#       name varchar(50) not null,
omm(#       age  int default 20,
omm(# omm(#      );      primary key(id)

NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "test666_pkey" for table "test666"
CREATE TABLE
omm=# \d test666
           Table "public.test666"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "test666_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

omm=# \d test666
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "test666_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#            Table "public.test666"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null

omm=# alter table test666 add column sex Boolean;
omm=# ALTER TABLE
omm=# 

omm=# \d test666
           Table "public.test666"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
 sex    | boolean               | 
Indexes:
    "test666_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

2.删除表中的已有字段

omm=# alter table test666 drop column sex ;
ALTER TABLE
omm=# \d test666
           Table "public.test666"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "test666_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

image.png

3.删除表的已有约束、添加约束

omm=# alter table test666 drop constraint test666_pkey;
omm=# ALTER TABLE

omm=# \d test666
           Table "public.test666"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20

omm=# select * from pg_constraint  where conname like 'test_pkey';
---------+--------------+---------+---------------+-------------+--------------+----------+----------+----------+-----------+-------------+-------------+------
---------+------------+-------------+--------------+---------+--------+--------+---------+-----------+-----------+-----------+-----------+--------+--------+---
-----------
(0 rows)

 conname | connamespace | contype | condeferrable | condeferred | convalidated | conrelid | contypid | conindid | confrelid | confupdtype | confdeltype | confm
atchtype | conislocal | coninhcount | connoinherit | consoft | conopt | conkey | confkey | conpfeqop | conppeqop | conffeqop | conexclop | conbin | consrc | co
nincluding 
omm=#

image.png

omm=# 
omm=# alter table test666 add constraint test666_pkey primary key(id);
NOTICE:  ALTER TABLE / ADD PRIMARY KEY will create implicit index "test666_pkey" for table "test666"
omm=# ALTER TABLE
omm=# 

omm=# select * from pg_constraint  where conname like 'test666_pkey';
   conname    | connamespace | contype | condeferrable | condeferred | convalidated | conrelid | contypid | conindid | confrelid | confupdtype | confdeltype | 
confmatchtype | conislocal | coninhcount | connoinherit | consoft | conopt | conkey | confkey | conpfeqop | conppeqop | conffeqop | conexclop | conbin | consrc
 | conincluding 
--------------+--------------+---------+---------------+-------------+--------------+----------+----------+----------+-----------+-------------+-------------+-
--------------+------------+-------------+--------------+---------+--------+--------+---------+-----------+-----------+-----------+-----------+--------+-------
-+--------------
 test666_pkey |         2200 | p       | f             | f           | t            |    16409 |        0 |    16415 |         0 |             |             | 
              | t          |           0 | t            | f       | f      | {1}    |         |           |           |           |           |        |       
 | 
(1 row)

omm=# \d test666
           Table "public.test666"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "test666_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

4.修改表字段的默认值

omm=# 
omm=# alter table test666 alter column age set default 25;
ALTER TABLE
omm=# \d test666
           Table "public.test666"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 25
Indexes:
    "test666_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

5.修改表字段的数据类型

omm=# alter table test666 ALTER COLUMN age TYPE bigint;
ALTER TABLE
omm=# \d test666
           Table "public.test666"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | bigint                | default 25
Indexes:
    "test666_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

6.修改表字段的名字

omm=# 
omm=# ALTER TABLE test666 RENAME COLUMN age TO stuage;
ALTER TABLE
omm=# \d test666
           Table "public.test666"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 stuage | bigint                | default 25
Indexes:
    "test666_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

7.修改表的名字

omm=# ALTER TABLE test666 RENAME TO my888;
ALTER TABLE
omm=# \d my888
            Table "public.my888"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 stuage | bigint                | default 25
Indexes:
    "test666_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

image.png

8.删除表

omm=# DROP TABLE my888;
DROP TABLE
omm=#

image.png

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最后修改时间：2022-12-10 15:41:36
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