带有条件的触发器trigger

再建好sequences 后，对oracle中的自增序列进行插入容易出现问题，

比如：用户如果在进行数据插入时指定了 CHATICON_SEQ.NEXTVAL 为自增ID，那么写好的触发器也会自动增加序列的，这样插入一条记录时，sequence就增加2个。为此需要在trigger中设置条件，设定当用户插入时id的值为空，才让触发器生效，这样可以避免序列重复增加。

以下是例子：

create or replace trigger trg_CHATICON
  before insert on CHATICON
  for each row
declare
nextid number;

begin
if :new.id is null then
  select CHATICON_SEQ.NEXTVAL into nextid FROM dual;
 :new.id := nextid;
end if;
end;

This entry was posted on 星期二, 9月 25th, 2007 at 10:11 上午 and is filed under DataBase. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.