创建触发器以插入到另一个表中 [英] Create trigger to insert into another table
问题描述
执行下面的触发器时遇到一些问题:
CREATE OR REPLACE TRIGGER AFTERINSERTCREATEBILL
AFTER INSERT
ON READING
FOR EACH ROW
DECLARE
varReadNo Int;
varMeterID Int;
varCustID Varchar(10);
BEGIN
SELECT SeqReadNo.CurrVal INTO varReadNo FROM DUAL;
Select MeterID INTO varMeterID
From Reading
Where ReadNo = varReadNo;
Select CustID INTO varCustID
From Address A
Join Meter M
on A.postCode = M.postCode
Where M.MeterID = varMeterID;
INSERT INTO BILL VALUES
(SEQBILLNO.NEXTVAL, SYSDATE, 'UNPAID' , 100 , varCustID , SEQREADNO.CURRVAL);
END;
错误消息:
*原因:触发器(或在其中引用的用户定义的plsql函数
此语句)试图查看(或修改)
在被触发它的语句修改的过程中.
*操作:重写触发器(或函数),使其不读取该表.
这是否意味着我不应该从表Reading中检索任何详细信息?
我认为在插入值时从Table Reading检索数据时会发生此问题:
SELECT SeqReadNo.CurrVal INTO varReadNo FROM DUAL;
Select MeterID INTO varMeterID
From Reading
Where ReadNo = varReadNo;
总有办法解决吗?还是有更好的方法来做到这一点?输入表Reading后,我需要在表BILL中插入新行,其中ReadNo需要引用我刚刚插入的ReadNo.
您无法在行触发器中从同一表中检索记录.您可以使用:new和:old从实际记录中访问值(这是您的情况吗?).然后可以将触发器重写为
CREATE OR REPLACE TRIGGER AFTERINSERTCREATEBILL
AFTER INSERT
ON READING
FOR EACH ROW
DECLARE
varCustID Varchar(10);
BEGIN
Select CustID INTO varCustID
From Address A
Join Meter M
on A.postCode = M.postCode
Where M.MeterID = :new.MeterID;
INSERT INTO BILL VALUES
(SEQBILLNO.NEXTVAL, SYSDATE, 'UNPAID' , 100 , varCustID , SEQREADNO.CURRVAL);
END;
如果需要从READING表中查询其他记录,则必须使用语句触发器,行触发器和PLSQL集合的组合.很好的例子是在 AskTom.oracle.com >
I have some problem executing the trigger below:
CREATE OR REPLACE TRIGGER AFTERINSERTCREATEBILL
AFTER INSERT
ON READING
FOR EACH ROW
DECLARE
varReadNo Int;
varMeterID Int;
varCustID Varchar(10);
BEGIN
SELECT SeqReadNo.CurrVal INTO varReadNo FROM DUAL;
Select MeterID INTO varMeterID
From Reading
Where ReadNo = varReadNo;
Select CustID INTO varCustID
From Address A
Join Meter M
on A.postCode = M.postCode
Where M.MeterID = varMeterID;
INSERT INTO BILL VALUES
(SEQBILLNO.NEXTVAL, SYSDATE, 'UNPAID' , 100 , varCustID , SEQREADNO.CURRVAL);
END;
Error Message:
*Cause: A trigger (or a user defined plsql function that is referenced in
this statement) attempted to look at (or modify) a table that was
in the middle of being modified by the statement which fired it.
*Action: Rewrite the trigger (or function) so it does not read that table.
Does it mean that I am not suppose to retrieve any details from table Reading?
I believe that the issue occur as I retrieving data from Table Reading while it is inserting the value:
SELECT SeqReadNo.CurrVal INTO varReadNo FROM DUAL;
Select MeterID INTO varMeterID
From Reading
Where ReadNo = varReadNo;
It's there anyway to resolve this? Or is there a better method to do this? I need to insert a new row into table BILL after entering the table Reading where the ReadNo need to reference to the ReadNo I just insert.
You cannot retrieve records from the same table in a row trigger. You can access values from actual record using :new and :old (is this your case?). The trigger could then be rewritten to
CREATE OR REPLACE TRIGGER AFTERINSERTCREATEBILL
AFTER INSERT
ON READING
FOR EACH ROW
DECLARE
varCustID Varchar(10);
BEGIN
Select CustID INTO varCustID
From Address A
Join Meter M
on A.postCode = M.postCode
Where M.MeterID = :new.MeterID;
INSERT INTO BILL VALUES
(SEQBILLNO.NEXTVAL, SYSDATE, 'UNPAID' , 100 , varCustID , SEQREADNO.CURRVAL);
END;
If you need to query other record from READING table you have to use a combination of statement triggers, row trigger and a PLSQL collection. Good example of this is on AskTom.oracle.com
这篇关于创建触发器以插入到另一个表中的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!