select round((to_date(to_char(end_date,'yyyy-mm-dd')||' '||to_char(end_time,'hh24:mi:ss'),'yyyy-mm-dd hh24:mi:ss')-to_date(to_char(start_date,'yyyy-mm-dd')||' '||to_char(start_time,'hh24:mi:ss'),'yyyy-mm-dd hh24:mi:ss'))*60)
from table name
where ......