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我正在尝试编写此触发器，但它无法正常工作。我有一张 GIVING 表（捐赠者、接收者、礼物名称）和一张 PERSONS 表（pname、年龄、头发颜色）。对于触发器，我希望它在捐赠者和接收者的头发颜色相同时吐出一条消息。微不足道，我知道，但我刚刚开始学习触发器并且完全坚持为什么这不起作用。谢谢。

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;

我收到的错误消息是执行期间错误“精确提取返回的行数超过请求的行数”，指向 DECLARE ... 下面的行？

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2 回答 2

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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？

于 2012-12-21T18:43:00.517 回答
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您没有将查询限制为插入/更新行的捐赠者/接收者。它们应该如下所示：

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

顺便说一句：您的触发器仅在 上触发INSERT OR UPDATE OF GIFTNAME，而它应该在上触发INSERT OR UPDATE OF donor, receiver并且您需要使用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;
于 2012-12-21T18:40:03.110 回答