Subtract Time from Time

Question

Dear Sir,
I want to subtract Time from time, Please help me
SELECT A.EMP_CODE,
TO_DATE(A.INTIME,'DD/MM/RR')IN_DATE
,MIN(TO_CHAR(A.INTIME,'HH24:MI')) IN_TIME
,MAX(TO_CHAR(A.OUTTIME,'HH24:MI')) OUT_TIME
,TRUNC(SUM(A.TDAYS)*24)||':'||TRUNC((SUM(A.TDAYS)*24-TRUNC(SUM(A.TDAYS)*24))*60) TOTAL_TIME
FROM HCM.EINOUT A, HCM.PERSONNEL B
     WHERE A.EMP_CODE = B.EMP_CODE AND
     TO_DATE(A.INTIME,'DD/MM/RR')BETWEEN
     TO_DATE('01/08/12','DD/MM/RR') AND TO_DATE('15/08/12','DD/MM/RR')
     AND B.DEPT_CODE = 16 and a.emp_Code = '09833'
     GROUP BY A.EMP_CODE, TO_DATE(A.INTIME,'DD/MM/RR')--, a.tdays
     ORDER BY 1, 2 ASC;
I want to subtract 20:00 from (out_time) column from every record
If I subtract it from first record then result in over_time column will be 2:46
(out_time - 20:00)
--------------Out put........................
code date in_time out_time total_time over_time
09833     02-AUG-12     09:18     22:46     13:28
09833     03-AUG-12     09:16     21:50     12:34
09833     04-AUG-12     09:28     21:41     12:13
thanks

Answer 1

this will help
--And if difference can be > 24 hours:
WITH t AS
     (SELECT TO_DATE ('26-aug-2011 10:10:10',
                      'dd-mon-yyyy hh24:mi:ss'
                     ) start_date_time,
             TO_DATE ('26-aug-2011 10:12:10',
                      'dd-mon-yyyy hh24:mi:ss'
                     ) end_date_time
        FROM DUAL)
SELECT    TRUNC (end_date_time - start_date_time)
       || ' days '
       || TO_CHAR (TRUNC (SYSDATE) + (end_date_time - start_date_time),
                   'hh24:mi:ss'
                  ) time_diff
  FROM t
--Or interval based solution for < 24 hour diff:
WITH t AS
     (SELECT TO_DATE ('26-aug-2011 10:10:10',
                      'dd-mon-yyyy hh24:mi:ss'
                     ) start_date_time,
             TO_DATE ('26-aug-2011 10:12:10',
                      'dd-mon-yyyy hh24:mi:ss'
                     ) end_date_time
        FROM DUAL)
SELECT REGEXP_SUBSTR (NUMTODSINTERVAL (end_date_time - start_date_time, 'day'),
                      '\d\d:\d\d:\d\d'
                     ) time_diff
  FROM t
--interval based solution for >= 24 hour diff:
WITH t AS
     (SELECT TO_DATE ('26-aug-2011 10:10:10',
                      'dd-mon-yyyy hh24:mi:ss'
                     ) start_date_time,
             TO_DATE ('26-aug-2011 10:12:10',
                      'dd-mon-yyyy hh24:mi:ss'
                     ) end_date_time
        FROM DUAL)
SELECT REGEXP_REPLACE (NUMTODSINTERVAL (end_date_time - start_date_time,
                                        'day'),
                       '^.0*(\d+) (.{8}).+$',
                       '\1 days \2'
                      ) time_diff
  FROM t
--another method
SELECT    TO_CHAR (TRUNC (nb_sec / 3600), '00')
       || ':'
       || TO_CHAR (nb_min - TRUNC (nb_sec / 3600) * 60, '00')
       || ':'
       || TO_CHAR (MOD (nb_sec, 60), '00')
  FROM (SELECT (end_date_time - start_date_time) * 24 * 3600 nb_sec,
               (end_date_time - start_date_time) * 24 * 60 nb_min
          FROM ps_tb_ln_pdc_status_log)
--another method
SELECT SYSDATE + 3.45 / 24 AS "End Date", SYSDATE AS "Start Date",
       CAST (SYSDATE + 3.45 / 24 AS TIMESTAMP) - SYSDATE AS "Duration"
  FROM DUAL;Regards,
friend.