c# - C# SQL 查询产生与 Management Studio 不同的结果

Question

SELECT  
   wl.WatchListId, wl.Code, wl.[Description], wl.DateCreated,
   wl.CreatedBy, wl.DateModified, wl.ModifiedBy,
   wpi.ParameterExpression as IndividualExpression,
   wpb.ParameterExpression as BusinessExpression,
   wpd.ParameterExpression as DefaultExpression,
   CASE 
       WHEN EXISTS(SELECT 1 FROM SourceWatchList 
                   WHERE SourceId = @SourceId AND WatchListId = wl.WatchListId)  
       THEN 1 ELSE 0 
   END AS IsActive
FROM 
   [WatchList] wl 
LEFT JOIN  
   SourceWatchList swl ON wl.WatchListId = swl.WatchListId AND swl.SourceId = @SourceId
LEFT JOIN 
   (SELECT 
        ParameterExpression, SourceId, WatchListId 
    FROM WatchListParameter 
    WHERE EntityType = 'INDIVIDUAL') wpi ON wpi.SourceId = @SourceId 
                                         AND wpi.WatchListId = wl.WatchListId
LEFT JOIN 
    (SELECT 
         ParameterExpression, SourceId, WatchListId 
     FROM WatchListParameter 
     WHERE EntityType = 'BUSINESS') wpb ON wpb.SourceId = @SourceId 
                                        AND wpb.WatchListId = wl.WatchListId
LEFT JOIN 
    (SELECT ParameterExpression, SourceId, WatchListId 
     FROM WatchListParameter 
     WHERE EntityType = 'DEFAULT') wpd ON wpd.SourceId = @SourceId 
                                       AND wpd.WatchListId = wl.WatchListId
WHERE 
     wl.IsActive = 1

我有上面的查询。很简单。

这是 SQL Server Management Studio 表中的一个片段：

并从 Visual Studio 中的调试器：

Visual Studio 表在 3 个表达式列中没有数据，而 Management Studio（正确）有。谁能告诉我为什么会这样，我可以采取哪些步骤来解决这个问题？

我 100% 确定我在两者之间也使用了相同的参数。

string sql = @"SELECT  wl.WatchListId,wl.Code,wl.[Description],wl.DateCreated,
                                wl.CreatedBy,wl.DateModified,wl.ModifiedBy,
                                wpi.ParameterExpression as IndividualExpression,
                                wpb.ParameterExpression as BusinessExpression,
                                wpd.ParameterExpression as DefaultExpression,
                                CASE WHEN EXISTS(Select 1 FROM SourceWatchList 
                                    WHERE SourceId = @SourceId AND WatchListId = wl.WatchListId)  
                                        THEN 1 ELSE 0 END AS IsActive
                        FROM [WatchList] wl 

                        LEFT JOIN  SourceWatchList swl on wl.WatchListId = swl.WatchListId and swl.SourceId = @SourceId
                        LEFT JOIN (Select ParameterExpression, SourceId, WatchListId FROM WatchListParameter WHERE EntityType = 'INDIVIDUAL') wpi
                                        ON wpi.SourceId = @SourceId AND wpi.WatchListId = wl.WatchListId
                        LEFT JOIN (Select ParameterExpression, SourceId, WatchListId FROM WatchListParameter WHERE EntityType = 'BUSINESS') wpb
                                        ON wpb.SourceId = @SourceId AND wpb.WatchListId = wl.WatchListId
                        LEFT JOIN (Select ParameterExpression, SourceId, WatchListId FROM WatchListParameter WHERE EntityType = 'DEFAULT') wpd
                                        ON wpd.SourceId = @SourceId AND wpd.WatchListId = wl.WatchListId
                        where wl.IsActive = 1";
        SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["WatchListCompliance"].ConnectionString);
        conn.Open();
        SqlCommand cmd = new SqlCommand(sql, conn);
        cmd.CommandText = sql;
        cmd.Parameters.AddWithValue("@SourceId", SourceId);

        DataTable dt = new DataTable();
        using (SqlDataAdapter a = new SqlDataAdapter(cmd))
        {
            a.Fill(dt);
        }

Answer 1

This might be a problem with types and equality. You can try using SqlDataType when you define the parameters on the sqlcommand. When you use addwithvalue without declaring a type it could be selecting the wrong type. Then you should use the type you declared in the sql expression.

cmd.Parameters.Add("@SourceId", SqlDbType.VarChar, 20);
cmd.Parameters["@SourceId"].Value = SourceId;

Answer 2

疯狂猜测：您确定您的会话配置方式相同吗？尤其是 SET ANSI_NULLS 选项，它改变了比较针对空值的行为方式。

值得注意的是，有些数据库可能有不寻常的默认值，但有些客户端（例如 ADO.NET）在连接时明确定义了自己的会话值，即使您没有要求他们这样做。