openGauss每日一练第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

1.测试准备

--首先创建一张测试表。
omm=# drop table if exists test;
NOTICE:  table "test" does not exist, skipping
DROP TABLE
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

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
--为表test新增一列，列名为sex，数据类型为Boolean：
omm=# alter table test add column sex Boolean;
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：
omm=# alter table test drop column sex ;
ALTER TABLE--执行下面gsql命令，再次查看表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

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：
omm=# alter table test drop constraint test_pkey;
ALTER TABLE
--执行下面的gsql命令，再次查看表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
--或直接查看约束是否被删除
omm=# 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 
---------+--------------+---------+---------------+-------------+--------------+----------+----------+----------+-----------+-------------+-------------+---------------+------------+------------
-+--------------+---------+--------+--------+---------+-----------+-----------+-----------+-----------+--------+--------+--------------
(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：
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--再次查看表test的信息：
omm=# select * from pg_constraint  where conname like 'test_pkey';
  conname  | connamespace | contype | condeferrable | condeferred | convalidated | conrelid | contypid | conindid | confrelid | confupdtype | confdeltype | confmatchtype | conislocal | coninhcou
nt | 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)

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

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
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
omm=#  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

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

8.修改表字段的名字

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

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：
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

10.删除表

omm=# DROP TABLE mytest;
DROP TABLE

课程作业

1.创建表，为表添加字段

omm=# create table xx1(
omm(#       id bigint,
omm(#       age  int default 20,
omm(#       name varchar(50) not null,
omm(#       primary key(id)
omm(#      );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "xx1_pkey" for table "xx1"
CREATE TABLE
omm=# \d xx1
             Table "public.xx1"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "xx1_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=# alter table xx1 add column sex Boolean;
ALTER TABLE
omm=# \d xx1
             Table "public.xx1"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
 sex    | boolean               | 
Indexes:
    "xx1_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

2.删除表中的已有字段

omm=# alter table xx1 drop column sex;
ALTER TABLE
omm=# \d xx1
             Table "public.xx1"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "xx1_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

3.删除表的已有约束、添加约束

omm=# alter table xx1 drop constraint xx1_pkey;
ALTER TABLE
omm=# \d xx1 
             Table "public.xx1"
 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 'xx1_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 
---------+--------------+---------+---------------+-------------+--------------+----------+----------+----------+-----------+-------------+-------------+---------------+------------+------------
-+--------------+---------+--------+--------+---------+-----------+-----------+-----------+-----------+--------+--------+--------------
(0 rows)

omm=# alter table xx1 add constraint xx1_pkey primary key(id);
NOTICE:  ALTER TABLE / ADD PRIMARY KEY will create implicit index "xx1_pkey" for table "xx1"
ALTER TABLE
omm=# select * from pg_constraint where conname like 'xx1_pkey';
 conname  | connamespace | contype | condeferrable | condeferred | convalidated | conrelid | contypid | conindid | confrelid | confupdtype | confdeltype | confmatchtype | conislocal | coninhcoun
t | connoinherit | consoft | conopt | conkey | confkey | conpfeqop | conppeqop | conffeqop | conexclop | conbin | consrc | conincluding 
----------+--------------+---------+---------------+-------------+--------------+----------+----------+----------+-----------+-------------+-------------+---------------+------------+-----------
--+--------------+---------+--------+--------+---------+-----------+-----------+-----------+-----------+--------+--------+--------------
 xx1_pkey |         2200 | p       | f             | f           | t            |    16403 |        0 |    16409 |         0 |             |             |               | t          |           
0 | t            | f       | f      | {1}    |         |           |           |           |           |        |        | 
(1 row)

omm=# \d xx1
             Table "public.xx1"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "xx1_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

4.修改表字段的默认值

omm=# alter table xx1 alter column age set default 25;
omm=# ALTER TABLE
omm=# \d xx1
             Table "public.xx1"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 25
Indexes:
    "xx1_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

5.修改表字段的数据类型

omm=# alter table xx1 alter COLUMN age type bigint;
ALTER TABLE
omm=# \d xx1
             Table "public.xx1"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | bigint                | default 25
Indexes:
    "xx1_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

6.修改表字段的名字

omm=# alter table xx1 rename COLUMN age to stuage;
ALTER TABLE
omm=# \d xx1
             Table "public.xx1"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 stuage | bigint                | default 25
Indexes:
    "xx1_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

7.修改表的名字

omm=# alter table xx1 rename TO xx2;
ALTER TABLE
omm=# \d xx2

omm=#              Table "public.xx2"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 stuage | bigint                | default 25
Indexes:
    "xx1_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

8.删除表

omm=# drop table xx2;
DROP TABLE