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スタックオーバーフロー！

私はMSSQLデータベースを持っています。このデータベースの一部は次の写真に示されています

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

私は、特定のevEventKindIDでイベントが発生した患者を見つけようとしている、複雑なクエリを作成しようとしています。たとえば、（evEventKindtID == 1）のイベントと（evEventKindID == 1）のイベントがある患者を検索したいと思います。

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());
      }
 }

問題は、次の反復ごとに前の反復よりも多くの要素が返される可能性があることです。それは私を悩ませます。クエリからのクエリは、最初のクエリよりも多くのエンティティをどのように返すことができますか？

SQL Server Profilerで、ADO.NETEFによって生成されたSQLクエリを見つけました。場所{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]

最初の反復の場所{2}：

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

そして、2回目の反復の{2}の場所：

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

この問題についてどう思いますか？

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1 に答える 1

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これは、との一般的な混乱foreachです。変数を参照するクエリは、パラメータがバインドされているときではなく、クエリが実行されたときにパラメータ値を取得します。だからあなたは持つことができます

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

あなたの場合、foreachループには1つの変数がありますlimit。あなたはそれを複数回参照しますが、それらの複数の参照はすべて同じ値を見ます。それがあなたが見る理由です

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

両方のパラメーターの値は31で、最初の反復からの29はなくなりました。

これを回避する最も簡単な方法は、毎回新しい変数を作成することです。

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 に答える