表的定義和修改：
Oracle的數據類型，函數，事物及失誤權限，表的約束
（表級定義，列級定義）
create table users(
ud number(4,0),
id number(3,-2),
nam char(32),
addrss varchar2(32),
birthday Date
);
rename users to users_;
rename users_ to users;
alter table users add(
add_col nvarchar2(12)
);
alter table users drop column add_col;
alter table users modify (
namvarchar2(64)
);
desc users;
drop table users;
//插入數據
insert intousers(ud,id,nam,addrss,birthday) values (1,156,'aaaa','aaa','12-9月-2012');
insert into users values(2,126,'bbbb','ccccc','11-9月-2012');
insert into users values(2,126,'bbbb','','11-9月-2012');
//查詢數據
select * from users;
SELECT nam ,dump(nam) FROM users whereud=1;
//更新數據
update users set nam='Andy' where ud=1;
update users set addrss='bbb' where ud=2;
update users set id=300;
update users set addrss='op' where addrssis null;
//刪除數據
delete users where ud=3;
序列：
/創建序列
create sequence seq
start with 1
increment by 1
minvalue 1
maxvalue 12000
cycle
nocache;
/使用seq
create table demo1(
idnumber primary key,
namevarchar2(32)
);
insert into demo1 values(seq.nextval,'andy');
select * from demo1;
