select id,
       case
         when t1 not between start_time and end_time then '1'
       end case
       || 
       case
         when t2 not between start_time and end_time then ',2'
       end case
       || 
       case
         when t3 not between start_time and end_time then ',3'
       end case
       ||
       case
         when t4 not between start_time and end_time then ',4'
       end case
       as time_not_between
     from tab;