Question

Dim invoiceCount As String =
        "SELECT COUNT(CustomerID) " &
        "FROM Invoices " &
        "WHERE CustomerID = @customerID"

    Dim selectCount As New OleDbCommand(invoiceCount, connection)
    selectCount.Parameters.AddWithValue("@customerID", customerID)

    Try
        connection.Open()
        Dim reader2 As OleDbDataReader = selectCount.ExecuteReader(CommandBehavior.SingleRow)

        If reader2.Read Then
            frmCustomerMaintenance.lblIncidents.Text = 'what do I put here?
        End If
        reader2.Close()
    Catch ex As OleDbException : Throw ex
    Finally : connection.Close()
    End Try

我一直在搞乱这一段时间，我尝试的所有内容都会返回错误。我对SQL仍然是相当新的但是需要这样做。我只想将查询结果存储在标签中，以显示客户输入的记录数量。

Answer 1

这是您要搜索的内容：

frmCustomerMaintenance.lblIncidents.Text = reader2[0].ToString()

Answer 2

嗯，要阅读第一列，您可以这样做：

frmCustomerMaintenance.lblIncidents.Text = reader.GetValue(0).ToString()

但是，如果您只是从一行中读取一列，那么只需拨打ExecuteScalar而不是ExecuteReader，就更容易了：

frmCustomerMaintenance.lblIncidents.Text = selectCount.ExecuteScalar().ToString()

在标签中显示SQL结果？

2 个答案: