openGauss每日一练第16天 | openGauss逻辑结构：表管理4

原创 xiaocx 2022-12-09

218

学习目标

学习openGuass数据库中如何对表进行修改

课程学习

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)
     );

执行过程如下：

[omm@opengauss ~]$ gsql -r
gsql ((openGauss 3.1.0 build 4e931f9a) compiled at 2022-09-29 14:19:24 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;
WARNING:  Session unused timeout.
FATAL:  terminating connection due to administrator command
no connection to the server
The connection to the server was lost. Attempting reset: Succeeded.
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=#

2.为表添加字段

--查看表test的信息
\d test

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

--执行下面gsql命令，查看表test的信息
\d test

执行过程如下：

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

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 ;

--执行下面gsql命令，再次查看表test的信息
\d test

执行过程如下：

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

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;

--执行下面的gsql命令，再次查看表test的信息：
\d test

--或直接查看约束是否被删除
select * from pg_constraint  where conname like 'test_pkey';

执行过程如下：

omm=# alter table test drop constraint test_pkey;
ALTER TABLE
omm=# \d test
             Table "public.test"
 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';
 conname | connamespace | contype | condeferrable | condeferred | convalidated | conrelid | c
ontypid | conindid | confrelid | confupdtype | confdeltype | confmatchtype | conislocal | con
inhcount | connoinherit | consoft | conopt | conkey | confkey | conpfeqop | conppeqop | conff
eqop | conexclop | conbin | consrc | conincluding 
---------+--------------+---------+---------------+-------------+--------------+----------+--
--------+----------+-----------+-------------+-------------+---------------+------------+----
---------+--------------+---------+--------+--------+---------+-----------+-----------+------
-----+-----------+--------+--------+--------------
(0 rows)

omm=#

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);

--再次查看表test的信息：
select * from pg_constraint  where conname like 'test_pkey';

\d test

执行过程如下：

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=# select * from pg_constraint  where conname like 'test_pkey';
  conname  | connamespace | contype | condeferrable | condeferred | convalidated | conrelid |
 contypid | conindid | confrelid | confupdtype | confdeltype | confmatchtype | conislocal | c
oninhcount | connoinherit | consoft | conopt | conkey | confkey | conpfeqop | conppeqop | con
ffeqop | conexclop | conbin | consrc | 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=#

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

执行过程如下：

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=#

7.修改表字段的数据类型

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

执行过程如下：

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=#

8.修改表字段的名字

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

执行过程如下：

mm=# 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=#

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

执行过程如下：

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=#

10.删除表

DROP TABLE mytest;

执行过程如下：

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

课程作业

1.创建表，为表添加字段
create table emp(id bigint,name varchar(50) not null,age int default 18,sex boolean,addr varchar(50),salary int,bz varchar(100),primary key(id));

\d emp
执行过程如下：

omm=# create table emp(id bigint,name varchar(50) not null,age int default 18,sex boolean,addr varchar(50),salary  int,bz varchar(100),primary key(id));
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "emp_pkey" for table "emp"
CREATE TABLE
omm=# 
omm=# \d emp
              Table "public.emp"
 Column |          Type          | Modifiers  
--------+------------------------+------------
 id     | bigint                 | not null
 name   | character varying(50)  | not null
 age    | integer                | default 18
 sex    | boolean                | 
 addr   | character varying(50)  | 
 salary | integer                | 
 bz     | character varying(100) | 
Indexes:
    "emp_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

2.删除表中的已有字段
alter table emp drop column bz;
\d emp
执行过程如下：

omm=# alter table emp drop column bz;
ALTER TABLE
omm=# \d emp
             Table "public.emp"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 18
 sex    | boolean               | 
 addr   | character varying(50) | 
 salary | integer               | 
Indexes:
    "emp_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#

3.删除表的已有约束、添加约束
alter table emp drop constraint emp_pkey;
\d emp
执行过程如下：

omm=# alter table emp drop constraint emp_pkey;
ALTER TABLE
omm=# \d emp
             Table "public.emp"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 18
 sex    | boolean               | 
 addr   | character varying(50) | 
 salary | integer               | 

omm=#

4.修改表字段的默认值
alter table emp alter column salary set default 5000;
\d emp
执行过程如下：

omm=# alter table emp alter column salary  set default 5000;
ALTER TABLE
omm=# \d emp
              Table "public.emp"
 Column |         Type          |  Modifiers   
--------+-----------------------+--------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 18
 sex    | boolean               | 
 addr   | character varying(50) | 
 salary | integer               | default 5000

omm=#

5.修改表字段的数据类型
alter table emp ALTER COLUMN salary TYPE bigint;
\d emp
执行过程如下：

omm=# alter table emp ALTER COLUMN salary  TYPE bigint;
ALTER TABLE
omm=# \d emp
              Table "public.emp"
 Column |         Type          |  Modifiers   
--------+-----------------------+--------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 18
 sex    | boolean               | 
 addr   | character varying(50) | 
 salary | bigint                | default 5000

omm=#

6.修改表字段的名字
ALTER TABLE emp RENAME COLUMN addr TO address;
\d emp
执行过程如下：

omm=# ALTER TABLE emp RENAME COLUMN addr TO address;
ALTER TABLE
omm=# \d emp
               Table "public.emp"
 Column  |         Type          |  Modifiers   
---------+-----------------------+--------------
 id      | bigint                | not null
 name    | character varying(50) | not null
 age     | integer               | default 18
 sex     | boolean               | 
 address | character varying(50) | 
 salary  | bigint                | default 5000

omm=#

7.修改表的名字
ALTER TABLE emp RENAME TO myemp;
\d myemp
执行过程如下：

omm=# ALTER TABLE emp RENAME TO myemp;
ALTER TABLE
omm=# \d myemp
              Table "public.myemp"
 Column  |         Type          |  Modifiers   
---------+-----------------------+--------------
 id      | bigint                | not null
 name    | character varying(50) | not null
 age     | integer               | default 18
 sex     | boolean               | 
 address | character varying(50) | 
 salary  | bigint                | default 5000

omm=#

8.删除表
drop table myemp;
执行过程如下：

omm=# drop table myemp;
DROP TABLE
omm=#

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openGauss每日一练

openGauss每日一练 第16天 | openGauss逻辑结构：表管理4

学习目标

课程学习

课程作业

文章被以下合辑收录

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openGauss每日一练第16天 | openGauss逻辑结构：表管理4