Question

这是我的插入和更新语句代码：

For i = 0 To lvFabric1.Items.Count - 1

            strQ4 = ""
            strQ4 = strQ4 & "INSERT into js_det(LINE_NO, FABRIC1, FABRIC2, `DESC`) SELECT LPAD('" & i + 1 & "',2, '0'), '" & lvFabric1.Items(i).Text & "','sdf', `DESC` from rm_inv where ITEM_CODE = '" & lvFabric1.Items(i).Text & "'"

            strQ5 = ""
            strQ5 = strQ5 & "UPDATE js_det set TRAN_NO = (SELECT JS_TRAN FROM counter) where Fabric1 = '" & lvFabric1.Items(i).Text & "'"

            cmd.CommandText = strQ4
            cmd.ExecuteNonQuery()

            cmd.CommandText = strQ5
            cmd.ExecuteNonQuery()

        Next

这里的问题是如果它循环5次以上它会变慢，需要3秒以上。我怎样才能加快这段代码的速度？还是有另一种方式？

感谢您的帮助。

Answer 1

为了加快速度，可以一次性完成所有事情，例如：

Dim sqls As New List(Of String)
For i = 0 To lvFabric1.Items.Count - 1
    sqls.Add("INSERT into js_det(LINE_NO, FABRIC1, FABRIC2, `DESC`) SELECT LPAD('" & i + 1 & "',2, '0'), '" & lvFabric1.Items(i).Text & "','sdf', `DESC` from rm_inv where ITEM_CODE = '" & lvFabric1.Items(i).Text & "'")

    sqls.Add("UPDATE js_det set TRAN_NO = (SELECT JS_TRAN FROM counter) where Fabric1 = '" & lvFabric1.Items(i).Text & "'")
Next
If sqls.Any() Then
    cmd.CommandText = sqls.Aggregate(Function(m, n) m & ";" & n)
    cmd.ExecuteNonQuery()
End If

但是，不建议在.net中进行sql查询。

应该使用SQL参数来避免任何sql注入或sql语法错误。

编辑：使用sql参数 -

    Using con As New SqlConnection("My connection string..."),
        cmd As New SqlCommand(sql, con)
        cmd.CommandText = "UPDATE js_det set TRAN_NO = (SELECT JS_TRAN FROM counter) where Fabric1 = @fabric"
        Dim fabricParam = cmd.Parameters.Add("@fabric", SqlDbType.VarChar)

        con.Open()
        For i = 0 To lvFabric1.Items.Count - 1
            fabricParam.Value = lvFabric1.Items(i).Text
            cmd.ExecuteNonQuery()
        Next
        con.Close()

    End Using

在mysql语句中使用For循环在vb.net中变慢

1 个答案: