想用更新觸發器更新多條記錄

Question

讓我解釋一下我的場景。 假設我在「Activities」表中有10條記錄，並帶有「EstimatedDate」列。每個記錄都是唯一的，並具有不同的「EstimatedDate」。這10條記錄都屬於同一個項目，具有相同的「ProjectId」。 如果我更改一行的「EstimatedDate」，它應該自動更改具有相同「ProjectId」的表中的以下行。

Answer 1

CREATE TRIGGER dbo.Activities_Update 
ON dbo.Activities 
AFTER UPDATE 
AS 
BEGIN 
    SET NOCOUNT ON; 
    UPDATE a 
    SET EstimatedDate = i.EstimatedDate 
    FROM dbo.Activities AS a 
    INNER JOIN inserted AS i 
    ON a.ProjectId = i.ProjectId 
    WHERE a.EstimatedDate <> i.EstimatedDate; 
END 
GO 

雖然這是不可能的，你UPDATE聲明是這樣的：

UPDATE Activities SET EstimatedDate = CASE 
    WHEN ActivityID = 1 THEN GETDATE() 
    WHEN ActivityID = 2 THEN DATEADD(DAY, 1, GETDATE()) END 
WHERE ProjectID = 1; 

如果你想要使用inserted的MAX日期，你可以說：

CREATE TRIGGER dbo.Activities_Update 
ON dbo.Activities 
AFTER UPDATE 
AS 
BEGIN 
    SET NOCOUNT ON; 

    ;WITH i AS (SELECT ProjectId, d = MAX(EstimatedDate) 
    FROM inserted GROUP BY ProjectId) 
    UPDATE a 
    SET EstimatedDate = i.d 
    FROM dbo.Activities AS a 
    INNER JOIN i 
    ON a.ProjectId = i.ProjectId 
    WHERE a.EstimatedDate <> i.d; 
END 
GO 

後者是未經測試。