上一次行更新

Question

上次使用日期列更新或插入行時記錄的最佳觸發是什麼？

我想這一點，但它不工作：

CREATE TRIGGER trUpdate ON Tablename FOR INSERT, UPDATE 
AS 

    IF @@nestlevel = 0 
    BEGIN 

    UPDATE Tablename 
     SET Datecolumn = GETDATE() 
     FROM 
    WHERE ID = (SELECT i.id FROM INSERTED i) 

    END 

Answer 1

你的語法只是一個小關：

CREATE TRIGGER dbo.trUpdate 
ON dbo.Tablename 
FOR INSERT, UPDATE 
AS 
BEGIN 
    SET NOCOUNT ON; 

    UPDATE Tablename 
    SET Datecolumn = GETDATE() 
    WHERE ID IN (SELECT id FROM inserted); 
END 
GO 

現在你應該做的是列更改爲NOT NULL和默認的GETDATE()。然後，您只需在更新時觸發此觸發器。

-- first clean up any remaining NULL values: 
UPDATE dbo.Tablename 
    SET DateColumn = '19000101' 
    WHERE DateColumn IS NULL; 

-- now add the default constraint: 
ALTER TABLE dbo.Tablename ADD CONSTRAINT 
    DF_Tablename_DateColumn DEFAULT(GETDATE()) FOR DateColumn; 

-- now add the NOT NULL constraint: 
ALTER TABLE dbo.Tablename ALTER COLUMN DateColumn 
    DATETIME NOT NULL; 

-- now you can update the trigger so that it only fires on update: 
ALTER TRIGGER dbo.trUpdate 
ON dbo.Tablename 
FOR UPDATE 
AS 
BEGIN 
    SET NOCOUNT ON; 

    UPDATE Tablename 
    SET Datecolumn = GETDATE() 
    WHERE ID IN (SELECT id FROM inserted); 
END 
GO 

Answer 2

你應該改變

UPDATE Tablename 
     SET Datecolumn = GETDATE() 
    WHERE ID = (SELECT i.id FROM INSERTED i) 

TO

IF NOT UPDATE(Datecolumn) 
UPDATE Tablename 
     SET Datecolumn = GETDATE() 
    WHERE ID IN (SELECT i.id FROM INSERTED i) 

由於插入的表可能conain多個enty。否則它應該工作正常。