ใช้คำสั่งอะไรในการแสดงข้อมูลที่มี วันเวลาที่มากที่สุด ของแต่ละกลุ่มครับ

select org.* 
from (select x, max(amount) as mx_amt from original group by x) as tmp
left join original as org on org.amount = tmp.mx_amt and org.x = tmp.x

SELECT  name_th , t1.nameP , t1.sm_pla_seed_sources , t1.s_pla_plant_area ,
                (SELECT GROUP_CONCAT(DATE_FORMAT(date_date,'%d/%m/%Y') ORDER BY date_date) FROM db_data_subdate WHERE data_id = t1.id AND date_type = 1 GROUP by data_id) as date_sapling,
                (SELECT GROUP_CONCAT(DATE_FORMAT(date_date,'%d/%m/%Y') ORDER BY date_date) FROM db_data_subdate WHERE data_id = t1.id AND date_type = 2 GROUP by data_id) as date_plant,
                max(t1.last_update) as time   ,
                 t1.sm_pla_plant_note
                FROM db_list_centers
                LEFT JOIN 
                (SELECT sv.name_th AS nameP  , 
                dc.sm_cor_centers , 
                dd.sm_pla_seed_sources , 
                dd.s_pla_plant_area , 
                DATE_FORMAT(dd.last_update ,'%Y/%m/%d'  '%H:%i:%S' ) AS last_update ,
               dd.id , 
               dd.sm_pla_plant_note
                FROM  db_data_cor dc, db_seed_varieties sv,  db_data_data dd 
                WHERE DC.id=DD.cor_id AND dc.sm_cor_year=  2560   AND dd.type=1 AND dc.sm_cor_seed_varieties=sv.id 
                AND dc.sm_cor_season =1 ) AS t1 ON db_list_centers.id = t1.sm_cor_centers GROUP BY NAME_TH