openGauss每日一练打卡第16天 | openGauss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

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)
     );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "test_pkey" for table "test"
omm=# CREATE TABLE

2.为表添加字段

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

--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

--执行下面gsql命令，查看表test的信息
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

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 ;
ALTER TABLE
--执行下面gsql命令，再次查看表test的信息
\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_default4.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
             Table "public.test"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
--或直接查看约束是否被删除
select * from pg_constraint  where conname like 'test_pkey';
 conname | connamespace | contype | condeferrable | condeferred | convalidated | conrelid | contypid | conindid | confrelid | 
confupdtype | confdeltype | confmatchtype | conislocal | coninhcount | connoinherit | consoft | conopt | conkey | confkey | co
npfeqop | conppeqop | conffeqop | conexclop | conbin | consrc | conincluding 
---------+--------------+---------+---------------+-------------+--------------+----------+----------+----------+-----------+-
------------+-------------+---------------+------------+-------------+--------------+---------+--------+--------+---------+---
--------+-----------+-----------+-----------+--------+--------+--------------
(0 rows)

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);
NOTICE:  ALTER TABLE / ADD PRIMARY KEY will create implicit index "test_pkey" for table "test"
ALTER TABLE
--再次查看表test的信息：
select * from pg_constraint  where conname like 'test_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 
-----------+--------------+---------+---------------+-------------+--------------+----------+----------+----------+-----------
+-------------+-------------+---------------+------------+-------------+--------------+---------+--------+--------+---------+-
----------+-----------+-----------+-----------+--------+--------+--------------
 test_pkey |         2200 | p       | f             | f           | t            |    16389 |        0 |    16395 |         0 
|             |             |               | t          |           0 | t            | f       | f      | {1}    |         | 
          |           |           |           |        |        | 
(1 row)
\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

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
             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

7.修改表字段的数据类型

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

8.修改表字段的名字

ALTER TABLE test RENAME COLUMN age TO stuage;
\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

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
            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

10.删除表

DROP TABLE mytest;
DROP TABLE

课程作业

1.创建表，为表添加字段

create table zhao(
      id bigint,
      name varchar(50) not null,
      age  int default 20,
      primary key(id)
     );
omm=# \d zhao
             Table "public.zhao"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "zhao_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=# alter table zhao add column address varchar(100);
ALTER TABLE
omm=# \d zhao
              Table "public.zhao"
 Column  |          Type          | Modifiers  
---------+------------------------+------------
 id      | bigint                 | not null
 name    | character varying(50)  | not null
 age     | integer                | default 20
 address | character varying(100) | 
Indexes:
    "zhao_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

2.删除表中的已有字段

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

3.删除表的已有约束、添加约束

alter table zhao drop constraint zhao_pkey;
omm=# \d zhao
             Table "public.zhao"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20

alter table zhao add constraint zhao_pkey primary key(id);
omm=# \d zhao
             Table "public.zhao"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "zhao_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

4.修改表字段的默认值

alter table zhao alter column age set default 30;
omm=#              Table "public.zhao"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 30
Indexes:
    "zhao_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default5.修改表字段的数据类型

alter table zhao alter column age type bigint;
omm=# \d zhao
             Table "public.zhao"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | bigint                | default 30
Indexes:
    "zhao_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

6.修改表字段的名字

omm=# alter table zhao rename COLUMN age TO niangling;
omm=# ALTER TABLE

omm=# \d zhao
              Table "public.zhao"
  Column   |         Type          | Modifiers  
-----------+-----------------------+------------
 id        | bigint                | not null
 name      | character varying(50) | not null
 niangling | bigint                | default 30
Indexes:
    "zhao_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

7.修改表的名字

omm=# alter table zhao rename to zhaozhumin;

omm=# \d zhaozhumin 
           Table "public.zhaozhumin"
  Column   |         Type          | Modifiers  
-----------+-----------------------+------------
 id        | bigint                | not null
 name      | character varying(50) | not null
 niangling | bigint                | default 30
Indexes:
    "zhao_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

8.删除表

omm=# drop table zhaozhumin ;
DROP TABLE