将varchar值'table'转换为数据类型int时转换失败-Java 学习之路

我正在创建多项选择题系统 . 到目前为止，我创建了这4个表和1个视图 .

这些表是tblQuestion，tblAnswer，tblQuiz，tblResult和tblResultDetail . tblQuestion是存储问题，tblAnswer用于存储问题的答案，tblResult用于记录每个回答测验的用户，并将用户答案存储在TblResultDetails中 .

根据以下代码，从视图中读取数据 . 我使用1,2,3,4，因为它是视图的列名 . 我这样做是为了随机化答案 .

Sub soalan()
    conn.Open()
        Dim myArr(3) As String
        Dim cmd As New SqlCommand("Select * From view_Soalan Where QuestionID=@IdSoalan", conn)
        cmd.Parameters.AddWithValue("@IdSoalan", Counter)
        Dim dr1 As SqlDataReader
        dr1 = cmd.ExecuteReader

        If dr1.Read() Then
        Me.lblSoalan.Text = dr1("QuestionTxt")
        Me.RadioButton1.Text = dr1("1")
        myArr(0) = dr1("1")
        Me.RadioButton2.Text = dr1("2")
        myArr(1) = dr1("2")
        Me.RadioButton3.Text = dr1("3")
        myArr(2) = dr1("3")
        Me.RadioButton4.Text = dr1("4")
        myArr(3) = dr1("4")

        Dim answerId As String

        If Me.RadioButton1.Checked = True Then
            answerId = dr1("1")


        ElseIf Me.RadioButton2.Checked = True Then
            answerId = dr1("2")

        ElseIf Me.RadioButton3.Checked = True Then
            answerId = dr1("3")

        ElseIf Me.RadioButton4.Checked = True Then
            answerId = dr1("4")

        End If

        'Dim jawapan As Integer = CInt(answerId)
        Session("jaw") = answerId

    Else
        conn.Close()
        Counter += 1
        soalan()
    End If
    conn.Close()
End Sub
Sub bersih()
    RadioButton1.Checked = False
    RadioButton2.Checked = False
    RadioButton3.Checked = False
    RadioButton4.Checked = False
End Sub

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

    soalan()
End Sub
Sub masuk()
    conn.Open()

    Dim cmdGetId As New SqlCommand("Select MAX(ResultId) From TblResult", conn)
    cmdGetId.ExecuteNonQuery()
    Dim drBaca As SqlDataReader
    drBaca = cmdGetId.ExecuteReader
    While drBaca.Read
        Dim maxID As Integer = drBaca(0)
        Session("maximum") = maxID
    End While



    conn.Close()
    conn.Open()

    Dim cmdInsert As New SqlCommand("Insert into TblResultDetail (ResultDetail_Result_Id,ResultDetail_Answer_Id) values ('" & Session("maximum") & "','" & Session("jaw") & "')", conn)
    cmdInsert.ExecuteNonQuery()
    conn.Close()
End Sub
End Class

我收到了错误

将varchar值'table'转换为数据类型int时转换失败 .

在cmdInsert命令中 . 我知道我不能直接将会话（“下巴”）插入表中 . 那么如何更换呢？

2 回答

在您的查询中，您引用整数：

... values（'“＆Session（”maximum“）＆”'，'“

只需删除引号即可 . 您也应该使用参数来防止SQL注入 .

即

Dim cmdInsert As New SqlCommand("Insert into TblResultDetail (ResultDetail_Result_Id,ResultDetail_Answer_Id) values (@max, @jaw)", conn)
cmdInsert.Parameters.AddWithValue("@max", Session("maximum"))
cmdInsert.Parameters.AddWithValue("@jaw", Session("jaw"))

回复于 2024-05-03T08:58:44+08:00

我认为你在某些字段中存储了错误的值 .

用这个

Public Module MyExtensions

    <System.Runtime.CompilerServices.Extension()> _
    Public Function IsInteger(ByVal value As String) As Boolean
        If String.IsNullOrEmpty(value) Then
            Return False
        Else
            Return Integer.TryParse(value, Nothing)
        End If
    End Function




<System.Runtime.CompilerServices.Extension()> _
Public Function ToInteger(ByVal value As String) As Integer
    If value.IsInteger() Then
        Return Integer.Parse(value)
    Else
        Return 0
    End If
End Function
   End Module

然后

value.ToInteger() < - 如果不是整数则返回0

您的代码中还有另一个错误 . 您应该在以开头的查询中使用ExecuteScalar而不是ExecuteNonQuery

“选择MAX（ResultId）......”

Dim cmdGetId As New SqlCommand("Select MAX(ResultId) From TblResult", conn)
 Dim maxID As Integer= cmdGetId.ExecuteScalar 
 Session("maximum") = maxID

ExecuteScalar 通常在查询返回单个值时使用 .

ExecuteNonQuery 通常用于没有结果的SQL语句（UPDATE，INSERT等） .

参考this

回复于 2024-05-03T08:58:44+08:00

将varchar值'table'转换为数据类型int时转换失败

2 回答

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