Taking Value from Database and Create XML FILE VIA C#

Well I produce code which takes the values from the database and creates XML files, but I stack on how to modify my code in order to avoid the empty cells from the column VALUES, also I need to select the data from the column VALUES where the column SELECT is 1. Can you please help me with examples? Thank you in advance .

My code :

public DataSet produceFieldsXml(int langID, int presID)
{
    SqlConnection con = new System.Data.SqlClient.SqlConnection();
    con.ConnectionString = ConfigurationManager.ConnectionStrings["beta"].ConnectionString;


    SqlDataAdapter da = new SqlDataAdapter(@"SELECT IsubField.ID,IsubField.SUBJECT_ID as SUBJECTID,IsubField.VALUE AS DSCR,IsubField.FIELD_TYPE_ID, PFTT.VALUE AS TITLE
                                              FROM I_SUBJECT_FIELD  IsubField, P_FIELD_TYPE_TITLE PFTT
                                              WHERE IsubField.PRESENTATION_ID = " + presID + @"
                                                    AND IsubField.LANGUAGE_ID = " + langID + @" 
                                                    AND PFTT.FIELD_TYPE_ID = IsubField.FIELD_TYPE_ID 
                                                    AND PFTT.LANGUAGE_ID = " + langID + @" 
                                             ORDER BY IsubField.SUBJECT_ID", con);

    DataSet ds = new DataSet();
    da.Fill(ds, "FieldItem");

    ds.Tables[0].Columns.Add("SEQ", typeof(Int64));

    DataSet dsNew = new DataSet();

    for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
    {
        SqlDataAdapter daII = new SqlDataAdapter(@"SELECT CATEGORY_ID FROM I_SUBJECT WHERE ID = " + Convert.ToInt32(ds.Tables[0].Rows[i]["SUBJECTID"].ToString().Trim()) + "", con);
        DataSet dsa = new DataSet();
        daII.Fill(dsa, "FieldItem");

        dsNew.Merge(dsa);
    }

    DataSet dsaa = new DataSet();
    for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
    {
        SqlDataAdapter daII = new SqlDataAdapter(@"SELECT SEQ FROM P_CATEGORY_FIELD WHERE CATEGORY_ID = " + Convert.ToInt32(dsNew.Tables[0].Rows[i]["CATEGORY_ID"].ToString().Trim()) + " AND FIELD_ID = " + Convert.ToInt32(ds.Tables[0].Rows[i]["FIELD_TYPE_ID"].ToString().Trim()) + "", con);
        daII.Fill(dsaa, "FieldItem");
        ds.Tables[0].Rows[i]["SEQ"] = dsaa.Tables[0].Rows[0]["SEQ"];                        
    }

    for (int i = 0; i > dsaa.Tables[0].Rows.Count; i++)
    {
        ds.Tables[0].Rows[i]["SEQ"] = dsaa.Tables[0].Rows[0]["SEQ"];         
    }

    dsaa.WriteXml(Server.MapPath("~/") + "ZipFiles\\" + "new.xml");

    return ds;
}