“参数?_1没有默认值"； ExecuteReader时出错 [英] "Parameter ?_1 has no default value" error when ExecuteReader

问题描述

Web服务中的以下代码有问题.寻找了解决方案，但是我所看到的似乎与我在下面所做的没什么不同.

Having problem with the code below in a web service. Have searched for a solution but nothing that I have seen seems different to what I am doing below.

注意:字符串变量'AccountNo'已传递到包含以下代码的函数中.

该错误在代码的最后一行ExecuteReader上生成.

The error is generated on the last line of code - ExecuteReader.

    Dim sConnString As String
    Dim rdr As OleDbDataReader
    Dim orderPaid As Decimal
    Dim fbeused As Decimal

    sConnString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source='c:\orders.mdb'"

    Dim conn As New OleDbConnection(sConnString)

    Dim sb As New StringBuilder
    sb.Append("SELECT DISTINCTROW OrderHeaders.Accountno, Sum(([paidqty]*[unitprice])*[orderheaders].[entpercent]/100) AS orderpaid, Sum([freeqty]*[unitprice]) AS fbeused")
    sb.Append(" FROM OrderHeaders INNER JOIN OrderDetails ON OrderHeaders.[OrderNo] = OrderDetails.[OrderNo]")
    sb.Append(" GROUP BY OrderHeaders.Accountno HAVING OrderHeaders.Accountno=?")
    Dim sqlString As String = sb.ToString

    Dim cmd As New OleDbCommand(sqlString, conn)
    cmd.CommandType = CommandType.Text
    'cmd.Parameters.AddWithValue("AccNo", AccountNo)
    cmd.Parameters.Add("AccNo", OleDbType.VarWChar).Value = AccountNo
    conn.Open()

    rdr = cmd.ExecuteReader()

我得到的错误是(如上所述)

The error I get is (as mentioned above)

Parameter ?_1 has no default value

推荐答案

问题实际上是错误的假设，那就是代码中有错误.

The question in fact had a wrong assumption and that was that there was an error in the code.

SQL查询的语法正确，并且已正确插入参数.但是，测试数据包含错误，因此正确格式的查询不会返回任何结果.

The syntax of the SQL query was correct and the parameter was being inserted correctly. However the test data contained errors and therefore no result was being returned by a correctly formatted query.

非常感谢您的输入.

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