SQL Server：插入，刪除後觸發

Question

請幫我用SQL語言中的觸發器。

我有2個表product_subcategories和Products。

• product_subcategories：id, name, count_products
• Products：id, name, price, id_product_subcategories

必要添加或刪除行產品表來更新子類別

例如產品數量時，我們有兩個子類別「name = first，count_products = 0」，「name = second，count_products = 0」。當添加到產品表格3行：「name = pr1，price = 1，id_product_subcategories = 1」，「name = np2，price = 2，id_product_subcategories = 1」，「name = PR3，price = 5，id_product_subcategories = 2」

表子類別應該

「NAME =第一，count_products = 2」， 「名稱=第二，count_products = 1」

這裏是我寫的，但出於某種原因，他沒有一個工作線，而我不明白該怎麼做，當你在插入的表中添加幾行來遍歷每行時？

CREATE TRIGGER 
    countproductscategories 
ON 
    dbo.products 
AFTER 
    INSERT 
AS 
IF @@ROWCOUNT = 1 
BEGIN 
    UPDATE dbo.product_subcategories 
    SET count_products = count_products + 1 
    WHERE dbo.product_subcategories.id = (SELECT id FROM inserted) 
END; 

Answer 1

什麼是@@ROWCOUNT = 1？這應該做你想要什麼：

CREATE TRIGGER 
    countproductscategories 
ON dbo.products AFTER INSERT 
AS 
BEGIN 
    UPDATE dbo.product_subcategories 
     SET count_products = count_products + 1 
     WHERE dbo.product_subcategories.id IN (SELECT id FROM inserted) 
END; 

如果你想在每次插入只有一行做到這一點，那麼你可以做：

CREATE TRIGGER 
    countproductscategories 
ON dbo.products AFTER INSERT 
AS 
BEGIN 
    UPDATE dbo.product_subcategories 
     SET count_products = count_products + 1 
     WHERE dbo.product_subcategories.id IN (SELECT id FROM inserted) AND 
       (SELECT COUNT(*) FROM inserted) = 1; 
END;