oracle alter table详解

ALTER TABLE (表名) ADD (列名 数据类型);

ALTER TABLE (表名) MODIFY (列名 数据类型);

ALTER TABLE (表名) RENAME COLUMN (当前列名) TO (新列名);

ALTER TABLE (表名) DROP COLUMN (列名);

ALTER TABLE (当前表名) RENAME TO (新表名)

create table dept(

deptno number(3) primary key,

dname varchar2(10),

loc varchar2(13)

);

create table employee_info(

empno number(3),

deptno number(3),

ename varchar2(10),

sex char(1),

phone number(11),

address varchar2(50),

introduce varchar2(100)

);

--

//0.重命名

//0.1 表:rename dept to dt;

rename dt to dept;

//0.2 列:alter table dept rename column loc to location;

alter tabledept rename column location to loc;

//1.添加约束

//1.1 primary key

alter table employee_info add constraint pk_emp_info primary key(empno);

//1.2 foreign key

alter table employee_info add constraint fk_emp_info foreign key(deptno)

references dept(deptno);

//1.3 check

alter table employee_info add constraint ck_emp_info check

(sex in ('F','M'));

//1.4 not null

alter table employee_info modify phone constraint not_null_emp_info not null;

//1.5 unique

alter table employee_info add constraint uq_emp_info unique(phone);

//1.6 default

alter table employee_info modify sex char(2) default'M';

//2.添加列

alter table employee_info add id varchar2(18);

alter table employee_info add hiredatedate default sysdate not null;

//3.删除列

alter table employee_info drop columnintroduce;

//3.修改列

//3.1 修改列的长度

alter table dept modify loc varchar2(50);

//3.2 修改列的精度

alter table employee_info modify empno number(2);

//3.3 修改列的数据类型

alter table employee_info modify sex char(2);

//3.4 修改默认值

alter table employee_info modify hiredate default sysdate+1;

//4.禁用约束

alter table employee_info disable constraintuq_emp_info;

//5.启用约束

alter table employee_info enable constraintuq_emp_info;

//6.延迟约束

alter table employee_info drop constraintfk_emp_info;

alter table employee_info add constraint fk_emp_info foreign key(deptno)

references dept(deptno)

deferrable initially deferred;

//7.向表中添加注释

comment on table employee_info is'information of employees';

//8.向列添加注释

comment on column employee_info.ename is'the name of employees';

comment on column dept.dname is'the name of department';

//9.清除表中所有数据

truncate table employee_info;

//10.删除表

drop table employee_info;

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