子查询返回的值超过1，即使它们没有返回任何内容

Question

我有一个像这样连接的数据库。

我正在编写一个WPF应用程序来对表进行简单的插入/删除/更新。

问题是这样的：

1. 我收到一个广告对象，并尝试将其插入到数据库

   中

   public static int Insert(Advertisement Advertisement)
   {
       Database db = new Database();
       db.Connect();
       SqlCommand command = db.CreateCommand(SQL_INSERT);
       PrepareCommand(command, Advertisement);
       int ret = db.ExecuteNonQuery(command);
       db.Close();
       return ret;
   }
   

SQL_INSERT

public static String SQL_INSERT = "INSERT INTO \"Advertisement\" VALUES (@IDProduct," +
        " @CampaignDescription, @CampaignStart, @CampaignEnd)";

IDAdvertisement是一个IDENTITY。

我在广告表INSERT

上设置了触发器

ALTER trigger [dbo].[AutomaticUserAdvertisementScoreCalculating]
ON [dbo].[Advertisement]
AFTER INSERT
AS
begin
begin transaction;
declare Users cursor for 
Select "User".IDUser, Sum(Price), inserted.IDProduct from "User"
join Purchase as pu on "User".IDUser = pu.IDUser  
join PurchaseProduct as pp on pu.IDPurchase = pp.IDPurchase
join Product as pr on pp.IDProduct = pr.IDProduct
join inserted on pr.IDProduct = inserted.IDProduct
where pr.ProductType = (select ProductType from Product
          join Advertisement on Product.IDProduct = Advertisement.IDProduct
          join inserted on Advertisement.IDProduct = inserted.IDProduct
          where Advertisement.IDAdvertisement = inserted.IDAdvertisement)
GROUP BY "User".IDUser, inserted.IDProduct
HAVING Sum(Price) > 50;
declare @IDUser int;
declare @Price decimal;
declare @IDProduct int;
open Users;
fetch next from Users into @IDUser,@Price, @IDProduct;
while @@FETCH_STATUS=0
begin
    insert into UserAdvertisementScore values(@IDUser, (select IDAdvertisement from Advertisement where IDProduct = @IDProduct), @Price);
    fetch next from Users into @IDUser, @Price, @IDProduct;
end
close Users;
deallocate Users;
commit;

端

我不知道为什么，但根据使用的IDProduct，它可能会抛出此错误。

  

子查询返回的值超过1。当子查询遵循=，！=，＆lt;，＆lt; =，＆gt;，＆gt; =或子查询用作表达式时，不允许这样做。   声明已经终止。

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Answer 1

我觉得这确实是重复的。当然错误是一回事，但这个问题的真正问题在于触发器存在严重缺陷。很确定你的整个触发器体可以简化为非常接近这个的东西。而且你不应该在触发器中使用事务。已经有一个正在进行的交易，您所做的任何事情都会导致原始交易失败。

insert UserAdvertisementScore
( --or whatever the column names are. You should ALWAYS specify the columns for an insert
    [User]
    , Price
    , IDProduct
)
Select u.IDUser
    , Sum(Price)
    , i.IDProduct 
from [User] u
join Purchase as pu on u.IDUser = pu.IDUser  
join PurchaseProduct as pp on pu.IDPurchase = pp.IDPurchase
join inserted i on pr.IDProduct = i.IDProduct
join Product as pr on pp.IDProduct = pr.IDProduct 
GROUP BY u.IDUser
    , i.IDProduct