I have two datagridviews. So for the second one, i just copy-pasted the code from the first and changed where the difference was. But i get an error at the secod data grid when i want to view the result of my sql code. Translated in english the error show something like that there was no value given to at least one required parameter. Please help! private void button1_Click(object sender, EventArgs e) {

        string connectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=save.mdb";

        try
        {

           database = new OleDbConnection(connectionString);
           database.Open();
           date =  DateTime.Now.ToShortDateString();
           string queryString = "SELECT zivila.naziv,(obroki_save.skupaj_kalorij/zivila.kalorij)*100 as Kolicina_v_gramih "
               + "FROM (users LEFT JOIN obroki_save ON obroki_save.ID_uporabnika=users.ID)"
               + " LEFT JOIN zivila ON zivila.ID=obroki_save.ID_zivila "
               + " WHERE users.ID= " + a.ToString();
           loadDataGrid(queryString);
       }
       catch (Exception ex)
       {
           MessageBox.Show(ex.Message);
           return;
       }
    }

    public void loadDataGrid(string sqlQueryString)
    {

        OleDbCommand SQLQuery = new OleDbCommand();
        DataTable data = null;
        dataGridView1.DataSource = null;
        SQLQuery.Connection = null;
        OleDbDataAdapter dataAdapter = null;
        dataGridView1.Columns.Clear(); // <-- clear columns

        SQLQuery.CommandText = sqlQueryString;
        SQLQuery.Connection = database;
        data = new DataTable();
        dataAdapter = new OleDbDataAdapter(SQLQuery);
        dataAdapter.Fill(data);
        dataGridView1.DataSource = data;
        dataGridView1.AllowUserToAddRows = false;
        dataGridView1.ReadOnly = true;
        dataGridView1.Columns[0].Visible = true;

    }

    private void Form8_Load(object sender, EventArgs e)
    {

    }

    private void button2_Click(object sender, EventArgs e)
    {
        string connectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=save.mdb";

        try
        {

            database = new OleDbConnection(connectionString);
            database.Open();
            date = DateTime.Now.ToShortDateString();
            string queryString = "SELECT skupaj_kalorij  "
                + "FROM obroki_save "
                + " WHERE users.ID= " + a.ToString();
            loadDataGrid2(queryString);
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
            return;
        }
    }

    public void loadDataGrid2(string sqlQueryString)
    {

        OleDbCommand SQLQuery = new OleDbCommand();
        DataTable data = null;
        dataGridView2.DataSource = null;
        SQLQuery.Connection = null;
        OleDbDataAdapter dataAdapter = null;
        dataGridView2.Columns.Clear(); // <-- clear columns

        SQLQuery.CommandText = sqlQueryString;
        SQLQuery.Connection = database;
        data = new DataTable();
        dataAdapter = new OleDbDataAdapter(SQLQuery);
        dataAdapter.Fill(data);
        dataGridView2.DataSource = data;
        dataGridView2.AllowUserToAddRows = false;
        dataGridView2.ReadOnly = true;
        dataGridView2.Columns[0].Visible = true;
    }