在使用 DECLARE 语句时尝试从 asp.net 传递参数，但收到错误提示 "Must declare the scalar variable "@pID”

Question

我有一个名为 ReportValues 的 table，它以键值对的形式存储有关玩家的所有信息。 table 有一个来自另一个名为 Reports 的 table 的外键。我试图为每个报告获取一行中的所有数据，其中键将是列名，值将填充返回的 table。如果我手动插入 @pID 而不是作为参数，那么代码可以工作，但是当使用参数时我会收到以下错误："Must declare the scalar variable "@pID”。这是我的代码：

public DataTable getBarChartData(int p_ID)        
{
    //this query is transposing rows into columns as each key gets a column and the grouping variable is RV.report
    string sqlQuery = "DECLARE @keyName AS VARCHAR(MAX) ";
    sqlQuery += "SELECT @keyName = ";
    sqlQuery += "COALESCE(@keyName + ', ', '') + CAST(keyName AS VARCHAR(20)) ";
    sqlQuery += "FROM(SELECT DISTINCT keyname FROM ReportValues) ActivePlayers ";
    sqlQuery += "SELECT @keyName keyNames ";
    sqlQuery += "DECLARE @DynamicPIVOT AS VARCHAR(MAX) ";
    sqlQuery += "SELECT @DynamicPIVOT = 'SELECT ' + @keyName + ";
    sqlQuery += "' FROM ( ";
    sqlQuery += "SELECT RV.report, RV.keyname, RV.value FROM ReportValues RV ";
    sqlQuery += "join ReportValues RV1 on RV.report = RV1.report ";
    sqlQuery += "join ReportValues RV2 on RV.report = RV2.report ";
    sqlQuery += "where RV1.value <> 1 and RV1.keyName = ''SessionStage'' and RV2.value =  @pID and RV2.keyName = ''PId'' and RV.report in ( ";
    sqlQuery += "SELECT id FROM Reports r ";
    sqlQuery += "WHERE r.timeStamp >= dateadd(hour, -240, GETDATE()) ";
    sqlQuery += ") ";
    sqlQuery += ") ActivePlayers";
    sqlQuery += "PIVOT(";
    sqlQuery += "MAX(value) FOR keyname IN(' + @keyName + ') ";
    sqlQuery += ") Result; ' ";
    sqlQuery += "EXEC(@DynamicPIVOT) ";
    int pID = p_ID;
    //this passes the query and param to an execution function
    DataTable dtLabels = GetBarChartDataByUser(sqlQuery, pID);
    return dtLabels;
}

//this is the sql execution function
public DataTable GetBarChartDataByUser(string strQuery, int pID)
{
    SqlConnection con = new SqlConnection(createConnectionReadOnly());
    con.Open();
    try
    {

        SqlCommand cmd = con.CreateCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = strQuery;
        cmd.Parameters.AddWithValue("@pID", pID);
        SqlDataAdapter dap = new SqlDataAdapter(cmd);
        //here is where I get the error
        DataSet ds = new DataSet();
        dap.Fill(ds);
        return ds.Tables[0];
    }
    catch (Exception ex)
    {

    }
    finally
    {
        if (con.State == ConnectionState.Open)
        {
            con.Close();
        }
    }
    return null;

}

Answer 1

"and RV2.value = @pID" 是动态字符串的一部分，不会被视为动态字符串构建查询中的变量。在 SQL 中，服务器变量范围仅扩展到当前正在执行的批处理或函数，因此在 "EXEC()" 中执行的动态构建代码不知道变量 @pID。
您可以通过几种方式解决问题，其中之一如下：

sqlQuery += "join ReportValues RV2 on RV.report = RV2.report ";
sqlQuery += "where RV1.value <> 1 and RV1.keyName = ''SessionStage'' and RV2.value =  @pID and RV2.keyName = ''PId'' and RV.report in ( ";
sqlQuery += "SELECT id FROM Reports r ";

到

sqlQuery += "join ReportValues RV2 on RV.report = RV2.report ";
sqlQuery += "where RV1.value <> 1 and RV1.keyName = ''SessionStage'' and RV2.value =  ' + CONVERT( VARCHAR, @pID ) + ' and RV2.keyName = ''PId'' and RV.report in ( ";
sqlQuery += "SELECT id FROM Reports r ";

(注意'+ @pID +')

另一个（我认为更好的方法）是替换：

"EXEC(@DynamicPIVOT) "

和

"EXEC sp_executesql @DynamicPIVOT, N'@pID INT', @pID "

注意： @DynamicPIVOT 必须声明为 NVARCHAR( MAX )
注2： 将@pID 声明为与RV2.keyName 相同的数据类型。这将避免在查询执行期间进行类型转换

为了帮助将来诊断类似问题，我建议您在执行 sqlQuery 之前检查它的值并将其粘贴到 SQL Management studio 中。这将清楚哪些部分是字符串，哪些部分是 SQL 可执行代码。

在使用 DECLARE 语句时尝试从 asp.net 传递参数，但收到错误提示 "Must declare the scalar variable "@pID”

Trying to pass parameters from asp.net when using a DECLARE statement but getting an error saying "Must declare the scalar variable "@pID"

asp.net

sql-server

tsql

scalar

sqlparameter