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堆栈溢出！

我有一个 MS SQL 数据库。该数据库的部分显示在下一张图片中

http://i.stack.imgur.com/DFnc5.png

我正在尝试进行可组合的查询，我正在尝试查找具有特定 evEventKindID 事件的患者。例如，我想查找具有 (evEventKindtID == 1) 事件和 (evEventKindID == 1) 事件的患者。

var query = from pt in db.tblPatient
            select pt;
var list = query.ToList();// {1}

foreach (var limit in group.limits.Values)
{
      if (limit.eventKind.Type == TypeOfEventKind.ekEvent)
      {
           query = from pt in query
           where (pt.tblEvent.Count(j => j.evEventKindID == limit.eventKind.ID) > 0)
                                select pt;// {2}

           list = query.ToList();
           MessageBox.Show(query.Count().ToString());
      }
 }

问题是每次下一次迭代都可以返回比上一次更多的元素。它让我感到困惑。查询中的查询如何返回比第一个查询更多的实体？

在 SQL Server Profiler 中，我找到了由 ADO .NET EF 生成的 SQL 查询。在位置 {1}：

SELECT 
[Extent1].[ptID] AS [ptID], 
[Extent1].[ptFullName] AS [ptFullName], 
[Extent1].[ptHomeAddress] AS [ptHomeAddress], 
[Extent1].[ptPhone] AS [ptPhone], 
[Extent1].[ptBirthDate] AS [ptBirthDate], 
[Extent1].[ptIsMale] AS [ptIsMale], 
[Extent1].[ptUserID] AS [ptUserID], 
[Extent1].[ptINN] AS [ptINN], 
[Extent1].[ptSNILS] AS [ptSNILS]
FROM [dbo].[tblPatient] AS [Extent1]

在第一次迭代的 {2} 位置：

exec sp_executesql N'SELECT 
[Project1].[ptID] AS [ptID], 
[Project1].[ptFullName] AS [ptFullName], 
[Project1].[ptHomeAddress] AS [ptHomeAddress], 
[Project1].[ptPhone] AS [ptPhone], 
[Project1].[ptBirthDate] AS [ptBirthDate], 
[Project1].[ptIsMale] AS [ptIsMale], 
[Project1].[ptUserID] AS [ptUserID], 
[Project1].[ptINN] AS [ptINN], 
[Project1].[ptSNILS] AS [ptSNILS]
FROM ( SELECT 
    [Extent1].[ptID] AS [ptID], 
    [Extent1].[ptFullName] AS [ptFullName], 
    [Extent1].[ptHomeAddress] AS [ptHomeAddress], 
    [Extent1].[ptPhone] AS [ptPhone], 
    [Extent1].[ptBirthDate] AS [ptBirthDate], 
    [Extent1].[ptIsMale] AS [ptIsMale], 
    [Extent1].[ptUserID] AS [ptUserID], 
    [Extent1].[ptINN] AS [ptINN], 
    [Extent1].[ptSNILS] AS [ptSNILS], 
    (SELECT 
        COUNT(1) AS [A1]
        FROM [dbo].[tblEvent] AS [Extent2]
        WHERE ([Extent1].[ptID] = [Extent2].[evPatientID]) AND ([Extent2].[evEventKindID] = @p__linq__0)) AS [C1]
    FROM [dbo].[tblPatient] AS [Extent1]
)  AS [Project1]
WHERE [Project1].[C1] > 0',N'@p__linq__0 int',@p__linq__0=29

在第二次迭代的 {2} 位置：

exec sp_executesql N'SELECT 
[Project2].[ptID] AS [ptID], 
[Project2].[ptFullName] AS [ptFullName], 
[Project2].[ptHomeAddress] AS [ptHomeAddress], 
[Project2].[ptPhone] AS [ptPhone], 
[Project2].[ptBirthDate] AS [ptBirthDate], 
[Project2].[ptIsMale] AS [ptIsMale], 
[Project2].[ptUserID] AS [ptUserID], 
[Project2].[ptINN] AS [ptINN], 
[Project2].[ptSNILS] AS [ptSNILS]
FROM ( SELECT 
    [Project1].[ptID] AS [ptID], 
    [Project1].[ptFullName] AS [ptFullName], 
    [Project1].[ptHomeAddress] AS [ptHomeAddress], 
    [Project1].[ptPhone] AS [ptPhone], 
    [Project1].[ptBirthDate] AS [ptBirthDate], 
    [Project1].[ptIsMale] AS [ptIsMale], 
    [Project1].[ptUserID] AS [ptUserID], 
    [Project1].[ptINN] AS [ptINN], 
    [Project1].[ptSNILS] AS [ptSNILS], 
    (SELECT 
        COUNT(1) AS [A1]
        FROM [dbo].[tblEvent] AS [Extent3]
        WHERE ([Project1].[ptID] = [Extent3].[evPatientID]) AND ([Extent3].[evEventKindID] = @p__linq__1)) AS [C1]
    FROM ( SELECT 
        [Extent1].[ptID] AS [ptID], 
        [Extent1].[ptFullName] AS [ptFullName], 
        [Extent1].[ptHomeAddress] AS [ptHomeAddress], 
        [Extent1].[ptPhone] AS [ptPhone], 
        [Extent1].[ptBirthDate] AS [ptBirthDate], 
        [Extent1].[ptIsMale] AS [ptIsMale], 
        [Extent1].[ptUserID] AS [ptUserID], 
        [Extent1].[ptINN] AS [ptINN], 
        [Extent1].[ptSNILS] AS [ptSNILS], 
        (SELECT 
            COUNT(1) AS [A1]
            FROM [dbo].[tblEvent] AS [Extent2]
            WHERE ([Extent1].[ptID] = [Extent2].[evPatientID]) AND ([Extent2].[evEventKindID] = @p__linq__0)) AS [C1]
        FROM [dbo].[tblPatient] AS [Extent1]
    )  AS [Project1]
    WHERE [Project1].[C1] > 0
)  AS [Project2]
WHERE [Project2].[C1] > 0',N'@p__linq__0 int,@p__linq__1 int',@p__linq__0=31,@p__linq__1=31

你怎么看这个问题？

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1 回答 1

1

这是与foreach. 引用变量的查询在执行查询时获取其参数值，而不是在绑定参数时。所以你可以拥有

int orderId = 1;
var query = from o in context.Orders where o.Id == orderId;
orderId = 2;
MessageBox.Show(query.Single().Id.ToString()); // shows that order 2 was retrieved

在您的情况下，您的foreach循环有一个变量limit。您多次引用它，但这些多次引用都看到相同的值。这就是为什么你看到

N'@p__linq__0 int,@p__linq__1 int',@p__linq__0=31,@p__linq__1=31

两个参数的值都是 31，第一次迭代的 29 消失了。

解决这个问题的最简单方法是每次创建一个新变量：

foreach (var limit in group.limits.Values)
{
    var locallimit = limit;
    // refer to locallimit in your query, not to limit
}
于 2012-09-02T18:27:57.983 回答