CREATE TABLE DATA (
  
  Visitor_Id         Varchar2(10),
  time1      TIMESTAMP
  
);

SELECT Visitor_Id,
count(case when (  time1 > SYSDATE - 30/1440)  then  1   end) "Less than 30 min",
         count(case when  (time1 > SYSDATE - 60/1440 and time1  < SYSDATE - 29/1440 ) then 1 end) "30 -60 Min",
         count(case when  (time1 > SYSDATE - 1440/1440 AND time1 < SYSDATE - 119/1440 ) then 1 end) "2 - 24 Hour"
 FROM  data GROUP BY Visitor_Id

count(case when  (TIME1 > SYSTIMESTAMP- INTERVAL ‘1440’ MINUTE AND TIME1  < SYSDATE – INTERVAL ‘120’ MINUTE ) then 1 end) "2 TO 24 HRS"

SELECT   Visitor_Id,
         COUNT(CASE 
                 WHEN (Time1 > sysTimesTamp - INTERVAL '60' MINUTE) THEN 1
               END) "< 1",
         COUNT(CASE 
                 WHEN Time1 > sysTimesTamp - INTERVAL '2' HOUR
                      AND Time1 <= sysTimesTamp - INTERVAL '1' HOUR THEN 1
               END) "1 TO 2",
         COUNT(CASE 
                 WHEN Time1 >= sysTimesTamp - INTERVAL '24' HOUR
                      AND Time1 <= sysTimesTamp - INTERVAL '2' HOUR THEN 1
               END) "2 TO 24",
         COUNT(CASE 
                 WHEN (Time1 < sysTimesTamp - INTERVAL '1' DAY) THEN 1
               END) "> 1 Day"
FROM     Date_Table
GROUP BY Visitor_Id
/