循环以在数据网格视图第2列中对数据进行计数 [英] Loop to count data in data grid view column 2

问题描述

Dim s As String = dgv.Rows(row).Cells("Column1").Value
             cmd = New OleDbCommand("SELECT COUNT(Protocol) As num FROM Raw_Protocol WHERE Protocol = '" & s & "'", connection)
        Dr = cmd.ExecuteReader

            While Dr.Read()


                dgv.Rows.Add()
                dgv.Rows(row).Cells("Column2").Value = Dr("num")
                   datagridview1.Rows(row).Cells("Column4").Value = Dr("num")
                row += 1

           End While

这是另一个问题，我想让它循环以仅在数据网格视图行第1列获得数据时才对mdb数据库中的数据进行计数，而在数据网格视图行第1列中没有数据时停止计数.可以向我展示我如何更改代码.谢谢

This is another question,i want to make it loop to count the data in the mdb database only when data grid view row column 1 got data and stop when the data grid view row column 1 don''t have data. Can show me how i changed the code.Thanks

推荐答案

不是答案，而是一个强烈的建议:永远不要将您的字符串连接起来以生成SQL命令:它是公开邀请您进行意外或故意的SQL注入攻击，这可能会破坏您的数据库.改用参数化查询:

Not an answer, but a strong suggestion: never, ever concatenate your strings to generate an SQL command: it is an open invitation to an accidental or deliberate SQL injection attack which can destroy your database. Use Parameterized queries instead:

cmd = New OleDbCommand("SELECT COUNT(Protocol) As num FROM Raw_Protocol WHERE Protocol = @PCL", connection)
cmd.Parameters.AddWithValue("@PCL", s);

您能正确解释您想要实现的目标吗?

Can you explain properly what you want to achieve?

如果我能得到您的帮助！

其在datagridview中的列表，其中显示了协议和协议计数，即

协议，计数
a，10
b，2

等等.如果是这样，您可以在查询中解决此问题

If I get what your after!

its a list in a datagridview that shows Protocol and Count of Protocol i.e.

Protocol, Count
a, 10
b, 2

and so on. If so you can solve this in a query

select protocol, count(protocol) from raw_protocol

如本文所示，将查询与数据适配器配合使用， oleDbAdapter [ ^ ]

该示例使用数据集，但您可以根据需要将其替换为数据表.

using the query with a dataadapter as shown in this article, oleDbAdapter[^]

The example uses a dataset but you can just replace it for a datatable if you wish.

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