创建触发器时提示表不存在？解决方法

create sequence product_log_seq     minvalue 1 maxvalue 99999999increment by 1start with 1;

create or replace trigger "product_log_tri"  before insert     on "i_product_log"    referencing new as new old as old    for each row      begin          select prodcut_log_seq.nextval into :new.pl_id from dual;      end;