使用编译错误和PL / SQL创建Oracle Trigger：ORA-02289：序列不存在

Question

我几天遇到这个问题，我从power designer生成以下sql，并在oracle运行它，但是它会抛出错误“Warning：Trigger created with compilation errors。”。

drop trigger "tib_material_classify"
/

create trigger "tib_material_classify" before insert
on "material_classify" for each row
declare
    integrity_error  exception;
    errno            integer;
    errmsg           char(200);
    dummy            integer;
    found            boolean;

begin
    --  column ""id"" uses sequence "seq_material_classify"
    select "seq_material_classify".Nextval into :new."id" from dual;

--  errors handling
exception
    when integrity_error then
       raise_application_error(errno, errmsg);
end;
/

和我显示错误，它抛出以下，我不知道我做错了什么，我需要你的帮助。非常感谢！

PL/SQL: SQL Statement ignored
10/12    PL/SQL: ORA-02289: sequence does not exist