select c.cod_mitem,b.rot_ord,b.Plan_wkhr_m,(sum(a.plan_wkhr_n) + sum(a.plan_wkhr_o))from web_wlms_o4sequence_user a  
        left join web_wlms_o3sequence b on a.rot_ord_id = b.id 
        left join web_wlms_o2order c on b.num_ord_id = c.id 
        group by c.cod_mitem,b.rot_ord,b.Plan_wkhr_m order by rot_ord 
 

public static DataTable GetAll()
{
   string sql = "select c.cod_mitem,b.rot_ord,b.Plan_wkhr_m,sum(a.plan_wkhr_n) from web_wlms_o4sequence_user a";
   sql = sql + string.Format("left join web_wlms_o3sequence b on a.rot_ord_id = b.id");
   sql = sql + string.Format("left join web_wlms_o2order c on b.num_ord_id = c.id");
   sql = sql + string.Format("where a.status ='01' group by c.cod_mitem,b.rot_ord,b.Plan_wkhr_m order by rot_ord");
   //string sql = "select user_id,user_nm,adr_r from web_user";
   DataTable dt = QueryHelper.QueryDataTable(sql);
   return dt;
}

string sql = "select c.cod_mitem,b.rot_ord,b.Plan_wkhr_m,sum(a.plan_wkhr_n) from web_wlms_o4sequence_user a ";
                sql = sql + string.Format(" left join web_wlms_o3sequence b on a.rot_ord_id = b.id ");
                sql = sql + string.Format(" left join web_wlms_o2order c on b.num_ord_id = c.id ");