Oracle创建触发器实现主键自增

create sequence seq_news;

CREATE OR REPLACE TRIGGER "SCOTT"."trigger_news" 
   before insert on "SCOTT"."NEWS_TABLE"
   for each row
begin
   if inserting then
      if :NEW."ID" is null then
         select seq_news.nextval into :NEW."ID" from dual;
      end if;
   end if;
end;
/
ALTER TRIGGER "SCOTT"."trigger_news" ENABLE;