How to update chart that linked to MySQL database?

Question

I have a chart that linked to MySQL database. I want to update the chart every second. I use the code below to load the Database to my chart :

private void button4_Click(object sender, EventArgs e)
    {
        MySqlConnection conDataBase = new MySqlConnection(constring);
        MySqlCommand cmdDataBase = new MySqlCommand(" select * from konsentrasi.okedeh ;", conDataBase);
        MySqlDataReader myReader;
        try
        {
            conDataBase.Open();
            myReader = cmdDataBase.ExecuteReader();

            while (myReader.Read())
            {
                chart1.Series["konsentrasi"].Points.AddXY(myReader.GetInt32("nomor"), myReader.GetInt32("konsentrasi"));
            }
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }

Then I use timer to update the chart :

chart1.Update();

But nothing in the chart changed. So, what should I do to update the chart? And how I can scroll the chart to load just some data. For example it only show 10 data?

Answer 1

You should add an ORDER clause to your SQL (probably DESC for some timestamp or ID) and a LIMIT clause to get only the last 10 records. Something like that:

SELECT * from konsentrasi.okedeh ORDER BY id DESC LIMIT 10; 

I hope it works for you.