Question

请用SQL语言帮我解决触发器。

我有2个表product_subcategories和Products。

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

在产品表中添加或删除行以更新子类别中的产品数量时是必要的

例如，我们有两个子类别＆＃34; name = first，count_products = 0＆＃34;，＆＃34; name = second，count_products = 0＆＃34;。当添加到产品表3行时：＆＃34; name = pr1，price = 1，id_product_subcategories = 1＆＃34;，＆＃34; name = np2，price = 2，id_product_subcategories = 1＆＃34;，＆＃34 ; name = PR3，price = 5，id_product_subcategories = 2＆＃34;

表子类别应该是

＆＃34; name = first，count_products = 2＆＃34;，＆＃34; name = second，count_products = 1＆＃34;

这是我写的内容，但由于某种原因，他不会在一行中工作，而且我不明白该怎么做，当你在插入的表中添加几行作为遍历每一行时？

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

什么是@@ROWCOUNT = 1？这应该做你想要的：

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;

如果您只想在插入一行时执行此操作，则可以执行以下操作：

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;

SQL Server：插入，删除后触发

1 个答案: