今天有同學過來問我mysql的儲存過程怎麼寫，我按我的經驗寫好了，call一下，也正確。
於是他問了下上次沒解決的觸發器怎麼做？我就思考了一番：覺得可以先試試上次寫了1個半小時的方法。
--- 觸發器：實現插入開始時間和結束時間自動生成執行時間
delimiter ;;
create trigger `inserttraininfo` before insert on `traininfo` for each row begin
declare curtime datetime;
select new.trainendtime - new.trainstarttime into curtime from traininfo where trainno=new.trainno limit 1;
set new.trainrunningtime = curtime;
end;;
delimiter ;
drop trigger if exists `inserttraininfo`;
delimiter ;;
create trigger `inserttraininfo` before insert on `traininfo` for each row begin
set new.trainrunningtime = sec_to_time(unix_timestamp(new.trainendtime) - unix_timestamp(new.trainstarttime ));
end;;
delimiter ;
time = sec_to_time(unix_timestamp(time2)- unix_timestamp(time1));