从 VB.NET 复选框选项构建 SQL 查询时遇到问题

Posted 2023-03-23

【中文标题】从 VB.NET 复选框选项构建 SQL 查询时遇到问题

【英文标题】：Trouble building an SQL Query from VB.NET checklistbox options

【发布时间】：2016-05-08 03:51:34

【问题描述】：

我正在尝试从 checkListBox 中选择的选项创建一个 sql 查询。用户将选择他们想要（在复选框中）包含数据的所有模块，然后它将构建查询以收集这些数据。他们还将输入将包含在查询中的评级值范围。我对使用 sql 很陌生，所以我很难理解最终查询中缺少什么运算符。

这是我目前拥有的：

    Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
    Dim h As Integer
    Dim queryString As String
    Dim moduleArray(6) As String
    Dim counter As Integer = 0
    Dim provider As String
    Dim database As String
    Dim connString As String
    Dim moduleLen As Integer = 0
    Dim moduleString As String = ""
    Dim sqlquery As New OleDb.OleDbCommand

    provider = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source ="
    Change the following to your access database location
    database = "C:\Users\mello_000\OneDrive\Google Drive\Computing\Exampapergenerator\users.accdb"
    connString = provider & database
    Dim myConnection As OleDbConnection = New OleDbConnection(connString)

    myConnection.Open()
    sqlquery.Connection = myConnection
    For h = 0 To h = 6
        For Each item As String In Me.CheckedListBox1.CheckedItems
            moduleArray(moduleLen) = item
            If moduleArray(moduleLen) = "" Then
            Else
                moduleLen = moduleLen + 1
            End If
        Next
    Next

    For i = 0 To moduleLen
        If i = 0 Then
            moduleString = "'" & moduleArray(i) & "'"
        ElseIf i > 0 Then
            moduleString = moduleString & "'OR'" + "'" & moduleArray(i) & "'"
        End If
    Next


    queryString = ("SELECT QText FROM Question WHERE QModule = '" & moduleString & "' AND QRating BETWEEN '" & TextBox1.Text() & "'AND'" & TextBox2.Text())
    sqlquery.CommandText = queryString
    sqlquery.ExecuteNonQuery()



End Sub

但是我得到的输出是："SELECT QText FROM Question WHERE QModule = ''C1''OR''C2'' AND QRating BETWEEN '1'AND'2" 和一个错误：

Syntax error (missing operator) in query expression 'QModule = ''C1''OR''C2'' AND QRating BETWEEN '1'AND'2'.

此外，以可打印的形式在编号列表中输出所有返回数据的最佳方式是什么？

【参考方案1】：

您为什么要这样做For h = 0 To h = 6 而不仅仅是For h = 0 To 6？

"'OR'" 周围不需要单引号，只需使用 " OR "。

而且你的 SQL 语法是错误的。这个QModule = ''C1''OR''C2'' 要么需要是QModule = 'C1' OR QModule = 'C2'，要么是更好的方式QModule IN ('C1','C2')

假设 QRating 是数字，则不需要单引号。这个QRating BETWEEN '1'AND'2' 应该是QRating BETWEEN 1 AND 2.

此外，您应该考虑使用 SQL 参数，这样如果您的数据中有引号，您就不必担心引号或转义它们。