假设一个这样的表：
tblCostCenters
CCID nvarchar(10) not null primary key
CCDesc nvarchar(100) null
现在有一个＆＃34; INSTEAD OF UPDATE＆＃34;触发此表。
触发器可以使用这些伪表：
inserted包含新记录，因为它们应该更新deleted包含更新前的旧记录现在，如果用户想要更新主键，会发生什么？
假设这句话：
UPDATE tblCostCenters set CCID='new' where CCID='old' ;
由于主键本身已更改，触发器如何匹配deleted和inserted之间的记录以找出应更新的记录？
答案 0 :(得分：3)
这没有神奇的伎俩 - 你只有inserted和deleted行来建立你的匹配。虽然我知道有（非常罕见的）更新PK可能有意义的情况（是的，是更新PK值的方法），你必须预测这样的情况并利用某种形式的备用密钥，这样即使PK更改也可以匹配行。
因此，如果你是PK是唯一的方式来唯一识别记录，那么当你改变时，你就会失去运气。如果您有另一个唯一约束（可用作备用键），那么只要PK更新就必须使用它。
总之，如果您要允许PK更改，我强烈建议您实施这种＆＃34;备份密钥＆＃34;处理这种情况和任何其他类似情况，并尽可能地限制首先发生这种情况的情况。
答案 1 :(得分：2)
你不能更新＆＃34;主键。主键IS记录本身。你所做的工作 - 正在删除＆＃34;未修改的pk＆＃34;并插入新的＆＃34;修改的pk＆＃34;。通过这种方式，可以清楚删除哪些记录以及插入哪些记录。
答案 2 :(得分：0)
要在@xdd answer上展开一点，这里有一些代码：
-- Find out [PK]s that have been "added"
SELECT [PK]
INTO #ToInsert
FROM inserted
EXCEPT
SELECT [PK]
FROM deleted
-- Find out [PK]s that have been "deleted"
SELECT [PK]
INTO #ToDelete
FROM deleted
EXCEPT
SELECT [PK]
FROM inserted
-- Change PK by deleting all records where PK is no longer present
-- and then inserting them as new records
DELETE FROM [Table]
WHERE [PK] IN( SELECT [PK] FROM #ToDelete )
INSERT INTO [Table]
SELECT *
FROM inserted
WHERE [PK] IN( SELECT [PK] FROM #ToInsert )
-- Update the rest of the data
UPDATE a
SET col1 = I.col1,
col2 = I.col2,
...
FROM [Table] AS a
INNER JOIN inserted AS I ON a.[PK] = I.[PK]
WHERE I.PK NOT IN( SELECT [PK] FROM #ToInsert )
AND I.PK NOT IN( SELECT [PK] FROM #ToDelete )
请注意，概念上不需要上次更新，因为您可以简单地进行更新
DELETE所有deleted和INSERT所有inserted IDENTITY
需要实际更新的唯一情况是，当您拥有/* ----------- iPhone 4 and 4S ----------- */
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