执行更新时提示错误：Oracle表xxx发生变化，数据库不能读它

触发器代码
create or replace trigger departmentUpdate
after update on departments for each row
begin
IF updating then
UPDATE employees
set departmentid = :new.departmentid
where departmentid = :old.departmentid;
end if;
end;
更新代码：
update departments set departmentid = 7 where departmentid = 1;

找到问题了，是因为其他触发器同时更新了employees表，希望其他人不要犯我同样的错误，么么哒