课程作业
1.创建表，为表添加字段
--创建表zouyang
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=# create table zouyang
omm-# ( id int ,
omm(# name varchar(20) not null,
omm(# age int default 20,
omm(# primary key(id)
omm(# );
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "zouyang_pkey" for table "zouyang"
CREATE TABLE
--为表zouyang增加字段sex
omm=# \d zouyang
Table "public.zouyang"
Column | Type | Modifiers
--------+-----------------------+------------
id | integer | not null
name | character varying(20) | not null
age | integer | default 20
Indexes:
"zouyang_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default
omm=# alter table zouyang add column sex boolean;
2.删除表中的已有字段
omm=# alter table zouyangdrop column sex ;
ALTER TABLE
omm=# \d zouyang
Table "public.zouyang"
Column | Type | Modifiers
--------+-----------------------+------------
id | integer | not null
name | character varying(20) | not null
age | integer | default 20
3.删除表的已有约束、添加约束
omm=# alter table zouyang add constraint yk_key primary key(id);
NOTICE: ALTER TABLE / ADD PRIMARY KEY will create implicit index "zy_key" for table "zouyang"
ALTER TABLE
omm=# \d zouyang
Table "public.zouyang"
Column | Type | Modifiers
--------+-----------------------+------------
id | integer | not null
name | character varying(20) | not null
age | integer | default 20
Indexes:
"zy_key" PRIMARY KEY, btree (id) TABLESPACE pg_default
4.修改表字段的默认值
omm=# alter table zouyang alter column age set default 25;
ALTER TABLE
5.修改表字段的数据类型
omm=# alter table zouyang ALTER COLUMN age TYPE bigint;
ALTER TABLE
6.修改表字段的名字
omm=# alter table zouyang RENAME COLUMN age TO stuage;
ALTER TABLE
omm=# \d zouyang
Table "public.zouyang"
Column | Type | Modifiers
--------+-----------------------+------------
id | integer | not null
name | character varying(20) | not null
stuage | bigint | default 25
Indexes:
"zy_key" PRIMARY KEY, btree (id) TABLESPACE pg_default
7.修改表的名字
omm=# ALTER TABLE zouyang rename to zy;
ALTER TABLE
omm=# \d zy
Table "public.zy"
Column | Type | Modifiers
--------+-----------------------+------------
id | integer | not null
name | character varying(20) | not null
stuage | bigint | default 25
Indexes:
"zy_key" PRIMARY KEY, btree (id) TABLESPACE pg_default
8.删除表
omm=# drop table zy;
DROP TABLE
omm=# \d zy
Did not find any relation named "zy".
