$query = mysql_query ("SELECT *
FROM tb_orderview
LEFT JOIN tb_order ON tb_orderview.od_id = tb_order.od_id
LEFT JOIN tb_product ON tb_orderview.pd_id = tb_product.pd_id
");
SELECT DISTINCT od_date
FROM tb_orderview
LEFT JOIN tb_order ON tb_orderview.od_id = tb_order.od_id
LEFT JOIN tb_product ON tb_orderview.pd_id = tb_product.pd_id