?? ?? ??: alter table tablename add(? ??? ?? [???][null/not null],….);

?? ?? ??: alter table tablename ??(? ??? ?? [???) value][null/not null],….);

?? ?? ??: alter table tablename drop(column);

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alter table? ???? ?? ??, ??, ???? ????.

??? ?? ??:
create table test1
(id varchar2(20) not null);

?? ??:

alter table test1
add (name varchar2(30) default ‘無名氏' not null);

SQL ?? ? ?? ??? ??? ?????.

alter table test1
add (name varchar2(30) default ‘無名氏' not null,
age integer default 22 not null,
has_money number(9,2)
);

?? ??

alter table test1
modify (name varchar2(16) default ‘unknown');

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-- Add/modify columns 
alter table TABLE_NAME rename column FIELD_NAME to NEW_FIELD_NAME;

?? ??

alter table test1
drop column name;

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?? ??,

insert into test1
values ('1′,'我們很愛你');

create table student (
studentid int primary key not null,
studentname varchar(8),
age int);

create table student (
studentid int primary key not null,
studentname varchar(8),
age int);

(2) ?? ??

create table students (
studentid int ,
studentname varchar(8),
age int,
constraint yy primary key(studentid));

???? ?? ? ?? ?? ??
??? ?? ?? ?? ?? pk_student ?? ?(studentid);

? ?? oracle ??? ?? ?? ? oracle ???? ?? ??? ??? ??? PHP ??? ????? ?????!