oracle基本语句整理

创建序列
create sequence SEQ_CARD_INFO_ID
minvalue 1
maxvalue 999999999999999999999999999
start with 1
increment by 1
cache 20;

添加列
alter table BIZ_ORDER add order_number number default 0;
comment on column BIZ_ORDER.order_number is '客户下单次数';

删除列
方法1：将一个列标识为unused，然后在系统负载比较轻的时候使用
alter table BIZ_ORDER set unused ("ORDER_NUMBER") cascade constraints;
alter table  BIZ_ORDER drop unused columns
方法2：适合应付比较小的表
alter table BIZ_ORDER  drop column ORDER_NUMBER