MSSQL 有效触发器 INSTEAD OF INSERT

Question

我有一个案例需要使用 instead-of-insert 触发器。我和我的同事想知道哪个更有效（内存使用、达到运行的时间等）。

触发器检查table中是否存在记录，如果不存在则插入新行，否则通过其键更新现有行。此示例中的主键是 (DocumentId, VatRate) 的组合键。

第一个变体是检查记录是否已经存在：

CREATE TRIGGER docvatsum_trg
ON DocumentVatSummary
INSTEAD OF INSERT
AS
BEGIN
      IF EXISTS (
         SELECT 1 FROM DocumentVatSummary a
         JOIN inserted b ON (a.DocumentId = b.DocumentId AND a.VatRate = b.VatRate)
      )
      BEGIN
         UPDATE DocumentVatSummary
         SET 
            DocumentVatSummary.VatBase = i.VatBase, 
            DocumentVatSummary.VatTotal = i.VatTotal
         FROM inserted i
         WHERE 
            DocumentVatSummary.DocumentId = i.DocumentId AND
            DocumentVatSummary.VatRate = i.VatRate
      END
      ELSE
      BEGIN
         INSERT INTO DocumentVatSummary
         SELECT * FROM inserted
      END
END;

第二个变体尝试插入，如果插入失败，则更新如下：

CREATE TRIGGER docvatsum_trg
ON DocumentVatSummary
INSTEAD OF INSERT
AS
BEGIN
   SAVE TRANSACTION savepoint
   BEGIN TRY
      INSERT INTO DocumentVatSummary
      SELECT * FROM inserted
   END TRY
   BEGIN CATCH
      IF XACT_STATE() = 1
         BEGIN
            ROLLBACK TRAN savepoint

            UPDATE DocumentVatSummary
            SET 
               DocumentVatSummary.VatBase = i.VatBase,
               DocumentVatSummary.VatTotal = i.VatTotal
            FROM inserted i
            WHERE 
               DocumentVatSummary.DocumentId = i.DocumentId AND
               DocumentVatSummary.VatRate = i.VatRate
         END
   END CATCH
END;

注意：需要回滚到保存点，因为 TSQL 中运行ning 事务中的 TRY-CATCH 实现。

哪个更好，为什么？如果您有更好的解决方案，请分享。

Answer 1

按照此处的说明在触发器中使用 MERGE：

MERGE SYNTAX

代码示例：

DECLARE @SummaryOfChanges TABLE(Change VARCHAR(20)); 

MERGE INTO Sales.SalesReason AS Target  
USING (VALUES ('Recommendation','Other'), 
              ('Review', 'Marketing'), 
              ('Internet', 'Promotion'))  
       AS Source (NewName, NewReasonType)  
ON Target.Name = Source.NewName  
WHEN MATCHED THEN  
UPDATE SET ReasonType = Source.NewReasonType  
WHEN NOT MATCHED BY TARGET THEN  
INSERT (Name, ReasonType) VALUES (NewName, NewReasonType)  
OUTPUT $action INTO @SummaryOfChanges;

MSSQL 有效触发器 INSTEAD OF INSERT

MSSQL effective trigger INSTEAD OF INSERT

tsql

sql-server

triggers

database-trigger