Which query will gives the exact one day difference:

Question

SELECT COUNT(*) AS tot FROM Test WHERE DATETIME BETWEEN TO_DATE('01/01/2012 12:00:00 AM', 'DD/MM/YYYY hh:mi:ss am') AND TO_DATE('01/02/2012 11:59:59 PM', 'DD/MM/YYYY hh:mi:ss am')
SELECT COUNT(*) AS tot FROM Test WHERE DATETIME BETWEEN TO_DATE('01/01/2012 00:00:00 AM', 'DD/MM/YYYY hh:mi:ss am') AND TO_DATE('01/01/2012 11:59:59 PM', 'DD/MM/YYYY hh:mi:ss am')

Answer 1

hI,
First lets assume that you did not mean to have the 1-feb-2012 in the last date of the first select.
SELECT COUNT(*) AS tot FROM Test WHERE DATETIME BETWEEN TO_DATE('01/01/2012 12:00:00 AM', 'DD/MM/YYYY hh:mi:ss am') AND
TO_DATE('01/02/2012 11:59:59 PM', 'DD/MM/YYYY hh:mi:ss am')
--           XXBut you want 1-jan-2012.
Then I would not use between for this but trunc for beter readability like:
TAB AS
select to_date('2012/01/01 00:00:00', 'YYYY/MM/DD HH24:MI:SS') DATETIME FROM DUAL union all
select to_date('2012/01/01 12:17:22', 'YYYY/MM/DD HH24:MI:SS') DATETIME FROM DUAL union all
select to_date('2012/01/01 23:59:59', 'YYYY/MM/DD HH24:MI:SS') DATETIME FROM DUAL union all
select to_date('2012/01/02 00:00:00', 'YYYY/MM/DD HH24:MI:SS') DATETIME FROM DUAL union all
select to_date('2012/01/02 12:17:21', 'YYYY/MM/DD HH24:MI:SS') DATETIME FROM DUAL
SELECT
  TO_CHAR(DATETIME,'YYYY/MM/DD HH24:MI:SS') DATETIME
FROM
  TAB
WHERE
  TRUNC(DATETIME) = to_date('2012/01/01', 'YYYY/MM/DD')
;You may look into an function based index on trunc(datetime) for preformance
Regards,
Peter