Question

下面的代码“”如果在“搜索按钮”中工作，但是我想在“加载表单”中使用它，当我运行它时应该自动将数据显示到datagridview中，这给出了上面提到的错误。任何建议将不胜感激。

 Private Sub Search_Record()
    Dim conn As New OleDbConnection
    Dim cmd As New OleDbCommand
    Dim da As New OleDbDataAdapter
    Dim dt As New DataTable
    Dim sSQL As String = String.Empty
    Try
        conn = New OleDbConnection(Get_Constring)
        conn.Open()
        cmd.Connection = conn
        cmd.CommandType = CommandType.Text
        sSQL = "SELECT Username, lname + ', ' + fname + ' ' + mname as name, password FROM Instructor"
        If Me.cboSearchBy.Text = "Name" Then
            sSQL = sSQL & " where lname + ', ' + fname + ' ' + mname like '%" & Me.txtSearch.Text & "%'"
            sSQL = sSQL & " and  level like '%instructor%'"
        Else
            sSQL = sSQL & " where Username =" & Me.txtSearch.Text
            sSQL = sSQL & " and  level like '%instructor%'"
        End If
        cmd.CommandText = sSQL
        da.SelectCommand = cmd
        da.Fill(dt)
        Me.dtgResult.DataSource = dt
        If dt.Rows.Count = 0 Then
            MsgBox("No record found!")
        End If
    Catch ex As Exception
        MsgBox(ErrorToString)
    Finally
        conn.Close()
    End Try
End Sub

Answer 1

当表单开始且txtSearch文本框中没有文本时，您的查询会出现语法错误。如果您使用了参数化查询，则可以避免此错误（更不用说家庭问题Sql Injection）

Using conn = New OleDbConnection(Get_Constring)
Using cmd = new OleDbComman()
    conn.Open()
    cmd.Connection = conn
    sSQL = "SELECT Username, lname + ', ' + fname + ' ' + mname as name, password FROM Instructor"
    If Me.cboSearchBy.Text = "Name" Then
       sSQL = sSQL & " where lname + ', ' + fname + ' ' + mname like ? and  level like ?"
    Else
       sSQL = sSQL & " where Username = ? and  level like ?"
    End If
    cmd.CommandText = sSQL
    cmd.Parameters.AddWithValue("@1", "%" & txtSearch.Text & "%")
    cmd.Parameters.AddWithValue("@2", "%instructor%")
    Using da = new OleDbDataAdapter(cmd)
       da.Fill(dt)
       Me.dtgResult.DataSource = dt
       If dt.Rows.Count = 0 Then
           MsgBox("No record found!")
       End If
    End Using
End Using

此外，如果您正在使用MS-Access数据库，请记住，PASSWORD是一个保留关键字，当您在上述查询中使用时，需要将其封装在方括号之间。

SELECT ......., [Password] ........

查询表达式中的语法错误缺少运算符“Username =和level like'％instructor％'

1 个答案: