在查询中使用 MAX(CASE WHEN) 出现奇怪的异常：DB2.iSeries.iDB2DCFunctionErrorException: '发生意外异常

Question

我有以下查询将行中的一些数据放在列中：

string qry3 =
            "SELECT TABLENAME1.SLONO AS ORDER, TABLENAME1.SLLNNO AS LINE " +
            ",  MAX(CASE WHEN TABLENAME2.CZVRNM in ('SLEEVEDEPTH', 'LENGTH') THEN CAST(RTRIM(TABLENAME2.CZREFD) AS FLOAT(53)) END) AS SLEEVE " +
            ",  MAX(CASE WHEN TABLENAME2.CZVRNM in ('INSTALLATION') THEN CAST(RTRIM(TABLENAME2.CZREFD) AS FLOAT(53)) END) AS DAMPER_AI " +
            "FROM LOCATION.LOCATION2.TABLENAME1 TABLENAME1 LEFT JOIN LOCATION.LOCATION2.TABLENAME2 TABLENAME2 " +
            "     ON (TABLENAME1.SLONO = TABLENAME2.SPONO AND TABLENAME1.SLLNNO = TABLENAME2.SPLNNO)  " +
            "GROUP BY TABLENAME1.SLONO, TABLENAME1.SLLNNO ";

但是当我尝试在以下代码中运行它时：

        try
        {
            conAS400.Open();

            iDB2Command command = conAS400.CreateCommand();
            command.CommandText = qry3;

            command.CommandTimeout = 0;

            iDB2DataReader reader = command.ExecuteReader();
            dtAS400 = new DataTable();
            dtAS400.Load(reader); //<-- The exception occurs here. I can't even catch it

            conAS400.Close();

            retrieved = true;
        }

        catch (Exception ex)
        {
            MessageBox.Show("Could not retrive the information. Exception: " + ex.Message);

            retrieved = false;
        }
        finally
        {
            conAS400.Close();
        }

我得到了这个例外：

"IBM.Data.DB2.iSeries.iDB2DCFunctionErrorException: '意外 发生异常。类型：System.AccessViolationException，消息： 尝试读取或写入受保护的内存。这通常是一个 指示其他内存已损坏..'"

我还有其他可以正常工作的查询，但这个不行。我什至尝试了如下 SQL 查询（感谢 Gordon Linoff 提供此代码）：

SELECT 
    A.IDA, A.SomeInfo,
    MAX(CASE WHEN VarName in ('Depth', 'Depth2') THEN VarValue END) AS Depth,
    MAX(CASE WHEN VarName in ('Length') THEN VarValue END) AS Length
FROM 
    A
LEFT JOIN 
    B ON A.IDA = B.IDA
GROUP BY 
    A.IDA, A.SomeInfo

而且它有效。我能做什么？

司机：

客户端访问 ODBC 驱动程序（32 位）12.00.00.00

iSeries Access ODBC 驱动程序 12.00.00.00

编辑：这是没有字符串的 sql 查询。

SELECT TABLENAME1.SLONO AS ORDER, TABLENAME1.SLLNNO AS LINE, 
    MAX(CASE WHEN TABLENAME2.CZVRNM in ('SLEEVEDEPTH', 'LENGTH') THEN CAST(RTRIM(TABLENAME2.CZREFD) AS FLOAT(53)) END) AS SLEEVE, 
    MAX(CASE WHEN TABLENAME2.CZVRNM in ('INSTALLATION') THEN CAST(RTRIM(TABLENAME2.CZREFD) AS FLOAT(53)) END) AS DAMPER_AI 
FROM LOCATION.LOCATION2.TABLENAME1 TABLENAME1 LEFT JOIN LOCATION.LOCATION2.TABLENAME2 TABLENAME2 
    ON (TABLENAME1.SLONO = TABLENAME2.SPONO AND TABLENAME1.SLLNNO = TABLENAME2.SPLNNO)  
GROUP BY TABLENAME1.SLONO, TABLENAME1.SLLNNO 

Answer 1

好的，所以我终于发现了问题所在。出于某种原因，我无法 CAST 在 MAX 内浮动。如果我从查询中删除两个CAST，异常就消失了，一切正常。我不确定为什么会发生这种情况，如果有人可以解释这一点，那将非常有帮助，因为我需要将这些值转换为浮动。另外，如果我SELECT 更多列，则有必要将所述列添加到GROUP BY 语句中。无论如何，这是修改后的代码：

编辑：找到施放它们的方法。事实证明，我得到了一些空值、一些空白字段，并且我试图将一个数字分配给一个字符串。这是现在的代码：

SELECT TABLENAME1.SLONO AS ORDER, TABLENAME1.SLLNNO AS LINE, TABLENAME1.PROMISEDT,
    CAST(MAX(CASE WHEN RTRIM(TABLENAME2.CZREFD) IS NULL OR RTRIM(TABLENAME2.CZREFD) = '' THEN '0.000' WHEN TABLENAME2.CZVRNM = 'SLEEVEDEPTH' OR TABLENAME2.CZVRNM = 'LENGTH' THEN RTRIM(TABLENAME2.CZREFD) END) AS FLOAT(53)) AS SLEEVE,  
    MAX(CASE WHEN TABLENAME2.CZVRNM in ('INSTALLATION') THEN RTRIM(TABLENAME2.CZREFD) END) AS DAMPER_AI 
FROM LOCATION.LOCATION2.TABLENAME1 TABLENAME1 LEFT JOIN LOCATION.LOCATION2.TABLENAME2 TABLENAME2 
    ON (TABLENAME1.SLONO = TABLENAME2.SPONO AND TABLENAME1.SLLNNO = TABLENAME2.SPLNNO)  
GROUP BY TABLENAME1.SLONO, TABLENAME1.SLLNNO, TABLENAME1.PROMISEDT --remember to add every column from the SELECT here