Question

我正在尝试编写此触发器，但它无法正常工作。我有一张桌子GIVING（捐赠者，接收者，礼物名称）和一张桌子PERSONS（pname，age，haircolor）。对于触发器，我希望它在捐赠者和接收者具有相同的头发颜色时吐出一条消息。琐碎，我知道，但我只是开始学习触发器而且完全坚持为什么这不会起作用。感谢。

create or replace TRIGGER SameHairColor
BEFORE INSERT OR UPDATE OF GIFTNAME ON GIVING
DECLARE
  haircolordonor varchar(255);
  haircolorreceiver varchar(255);
BEGIN
select persons.haircolor into haircolordonor
from persons, giving
where (donor = persons.pname);
select persons.haircolor into haircolorreceiver
from persons, giving
where (receiver = persons.pname);

if (haircolordonor = haircolorreceiver) then

dbms_output.put_line('Wow, they have the same haircolor!  Who would have thought?');
end if;

end;

我得到的错误信息是执行过程中的错误“确切提取返回超过请求的行数”，指向DECLARE下面的行...？

Answer 1

您不是将查询限制在插入/更新行的捐赠者/接收者。他们应该是这样的：

select persons.haircolor
into haircolordonor
from persons
where persons.pname = :NEW.donor;

顺便说一句：您的触发器仅在INSERT OR UPDATE OF GIFTNAME触发，而它应在INSERT OR UPDATE OF donor, receiver触发，您需要使用FOR EACH ROW。

您的触发器应如下所示：

CREATE OR REPLACE TRIGGER SameHairColor
BEFORE INSERT OR UPDATE OF donor, receiver ON GIVING
  FOR EACH ROW
DECLARE
  haircolordonor varchar(255);
  haircolorreceiver varchar(255);
BEGIN
  select persons.haircolor into haircolordonor
  from persons
  where (persons.pname = :NEW.donor);
  select persons.haircolor into haircolorreceiver
  from persons
  where (persons.pname = :NEW.receiver);

  IF (haircolordonor = haircolorreceiver) THEN
    dbms_output.put_line('Wow, they have the same haircolor!  Who would have thought?');
  END IF;
END;

Answer 2

CREATE OR REPLACE TRIGGER SameHairColor
BEFORE INSERT OR UPDATE OF GIFTNAME ON GIVING
REFERENCING NEW ROW AS new
FOR EACH ROW
DECLARE
  haircolordonor varchar(255);
  haircolorreceiver varchar(255);
BEGIN
select persons.haircolor into haircolordonor
from persons, giving
where (:new.donor = persons.pname);
select persons.haircolor into haircolorreceiver
from persons, giving
where (:new.receiver = persons.pname);

if (haircolordonor = haircolorreceiver) then
    dbms_output.put_line('Wow, they have the same haircolor!  Who would have thought?');
end if;

end;

也许这可能会有所帮助？

Oracle Trigger Simple SQL

2 个答案: