表基本信息修改

示例操作如下

--班级信息表
create table t_class_info(
classno number(3) primary key,
classname varchar2(10),
classplace varchar2(13)
);

--学生信息表
create table t_student_info(
stuno number(3),
classno number(3),
stuname varchar2(10),
stusex char(1),
stucontect number(11),
stuadd varchar2(50),
studetailinfo varchar2(100)
);

--重命名表
alter table t_class_infot rename to t_class_info

--修改列名
alter table t_class_info rename column classplace to location;

--添加主键约束
alter table t_student_info add constraint pk_stu_no primary key(stuno);

--添加外键约束
alter table t_student_info add constraint fk_classno foreign key(classno) references t_class_info(classno);

--添加check约束
alter table t_student_info add constraint ck_stu_info check (stusex in ('f','m'));

alter table ttt add constraint index_age check (age>0 and age<50)

--添加not null约束
alter table t_student_info modify stucontect constraint not_null_info not null;

--添加unique约束
alter table t_student_info add constraint uq_stu_contect unique(stucontect);

--添加default约束
alter table t_student_info modify stusex char(2) default'm';

--增加列
alter table t_student_info add stuid varchar2(18);
alter table t_student_info add stuage date default sysdate not null;

--删除列
alter table t_student_info drop column studetailinfo;

--修改列的长度，长度只能由小改成大，如果要改小，则要删除该字段下的值
alter table t_class_info modify classplace varchar2(50);

--修改列的精度
alter table t_student_info modify stuno number(2);

--修改列的数据类型
alter table t_student_info modify stusex char(2);

--修改列的默认值
alter table t_student_info modify stuage default sysdate+1;

--禁用约束
alter table t_student_info disable fk_classno;

--启用约束
alter table t_student_info enable fk_classno;

--删除约束,如果有外键约束则要先删除外键表中的
alter table t_student_info drop fk_classno;

--延迟约束
alter table t_student_info add constraint fk_classno foreign key(classno)
references t_class_info(classno)
deferrable initially deferred;

--向表中添加注释
comment on table t_student_info is '学生表';

--向列添加注释
comment on column t_student_info.stuname is '学生姓名';
comment on column t_class_info.classname is '班级';

--清除表中所有数据
truncate table t_student_info;
--删除表
drop table t_student_info;

--删除表不经过回收站
drop table t_student_info purge;

--闪回被删除的表
flashback table t_student_info to before drop;