主题：[求助] sql保存速度如何优化

    老师，以下是保存的代码，逐行判断和保存，行数多的话，很慢，有点假死的感觉，有没有什么方法优化一下。

    cmd.CommandText = "sele ct * from {明细} where  [_Identify] is null"
        Dim sdt As DataTable = cmd.ExecuteReader
       
        For Each dr As DataRow In dt.Se lect("ch > 0")
            cmd.CommandText = "sel ect Count(*) FROM {明细} where ItID = " & dr("ItID")
            Dim sz As String
            Dim lm As String           
            If cmd.ExecuteScalar > 0 Then
                For Each c As DataCol In sdt.DataCols
                    If c.Name <> "ch" AndAlso tb.Cols.Contains(c.Name) Then
                        If sz > "" Then sz &= ","
                        sz &= c.Name & " = '" & dr(c.Name) & "'"
                    End If
                Next
                cmd.CommandText = "UPD ATE {明细} SET " & sz & " WHERE ItID = " & dr("ItID")
                cmd.ExecuteNonQuery()
            Else
                For Each c As DataCol In sdt.DataCols
                    If c.Name <> "ch" AndAlso tb.Cols.Contains(c.Name) Then
                        If lm > "" Then lm &= ","
                        lm &= "[" & c.Name & "]"
                        If sz > "" Then sz &= ","
                        sz &= "'" & dr(c.Name) & "'"
                    End If
                Next
                cmd.CommandText = "Ins ert Into {明细} (" & lm & ") Values ( " & sz & ")"
                cmd.ExecuteNonQuery
            End If
            sz = Nothing
            lm = Nothing
        Next

  Dim udstr As String
        For Each dr As DataRow In dt.Sel ect("ch > 0")
            cmd.CommandText = "sel ect Count(*) FROM {明细} where ItID = " & dr("ItID")
            Dim sz As String
            Dim lm As String
            If cmd.ExecuteScalar > 0 Then
                For Each c As DataCol In sdt.DataCols
                    If c.Name <> "ch" AndAlso tb.Cols.Contains(c.Name) Then
                        If sz > "" Then sz &= ","
                        sz &= c.Name & " = '" & dr(c.Name) & "'"
                    End If
                Next
                If udstr > "" Then udstr &= " ; "
                udstr &= "UPD ATE {明细} SET " & sz & " WHERE ItID = " & dr("ItID")
            Else
                For Each c As DataCol In sdt.DataCols
                    If c.Name <> "ch" AndAlso tb.Cols.Contains(c.Name) Then
                        If lm > "" Then lm &= ","
                        lm &= "[" & c.Name & "]"
                        If sz > "" Then sz &= ","
                        sz &= "'" & dr(c.Name) & "'"
                    End If
                Next
                If udstr > "" Then udstr &= " ; "
                udstr &= "Insert Into {明细} (" & lm & ") Values ( " & sz & ")"
            End If
            sz = Nothing
            lm = Nothing
        Next
        MessageBox.Show(udstr)
        If udstr > "" Then
            cmd.CommandText = udstr
            cmd.ExecuteNonQuery
        End If

messaghebox显示出来的结果是 

此主题相关图片如下：无标题魂牵梦萦.png

结果显示错误为

.NET Framework 版本：4.0.30319.42000
Foxtable 版本：2020.1.19.19
错误所在事件：
详细错误信息：
在 SQL 语句结尾之后找到字符。

老师，Access 事务没有接触过，我应该从那里入手，想实现这样的功能需要学习那些知识？