Question

So i have a procedure that i’m currently in the process of debugging and i’ve narrowed it down to this select statement.

Note: where the to_date(”), 3300, 5220 is a representation of what would come from a parameter.

   SELECT SHIFT_ID_PK, SHIFT_NAME_FK,
         SHIFT_START_DAY, SHIFT_START_TIME,
         SHIFT_END_DAY, SHIFT_END_TIME, 
         SITE_ID_FK, SHIFT_DAY_ID,
         STARTOFFSET, ENDOFFSET,
         TO_TIMESTAMP_TZ((TO_DATE('3/13/2012 7:00 ', 'mm/dd/yyyy HH:MI:SS am') - (3300  / 24 / 60)) + (STARTOFFSET / 24 / 60),  'YYYY-MM-DD HH:MI:SS TZH:TZM') AS SHIFT_START_DATE,  
         TO_TIMESTAMP_tz((TO_DATE('3/14/2012 1:00 ', 'mm/dd/yyyy HH:MI:SS am') - (5220 / 24 / 60)) + (ENDOFFSET   / 24 / 60),  'YYYY-MM-DD HH:MI:SS TZH:TZM') AS SHIFT_END_DATE   
  from   shift_tbl
  WHERE
         ENDOFFSET >= 3300
  AND    STARTOFFSET < 5220 
  order by shift_start_date asc, shift_end_date;

Now what this is suppose to do, is take the parameter which is a timestamp and subtract an offset value.

this value represents the number of minutes that has gone by during the week where sunday at midnight = 0. (So if it was monday at midnight the offset would = 1440).

when the offset is subtracted from the parameter, you then get the beginning of the week. You then get the offset value from the table which was already predetermined and add that value to the start of the week to obtain the timestamp.

This is done in order to get the start date and end date of a shift.

now below you will see and example of a result set that would come from this:

 SHIFT_ID_PK SHIFT_NAME_FK SHIFT_START_DAY SHIFT_START_TIME SHIFT_END_DAY SHIFT_END_TIME SITE_ID_FK SHIFT_DAY_ID STARTOFFSET ENDOFFSET **SHIFT_START_DATE                               SHIFT_END_DATE**   
 6146        6206          3               23:00             4            7:00           2450        3            4260         4740      **11-MAR-13 11.00.00.000000000 PM -05:00        11-MAR-14 07.00.00.000000000 PM -05:00**

now my problem is that my shift_start_date and shift_end_date come out as the same value like so

 SHIFT_ID_PK SHIFT_NAME_FK SHIFT_START_DAY SHIFT_START_TIME SHIFT_END_DAY SHIFT_END_TIME SITE_ID_FK SHIFT_DAY_ID STARTOFFSET ENDOFFSET **SHIFT_START_DATE                               SHIFT_END_DATE**   
 6146        6206          3               23:00             4            7:00           2450        3            4260         4740      **11-MAR-13 11.56.00.000000000 PM -05:00        11-MAR-13 11.56.00.000000000 PM -05:00**

The values marked with

 **.....**

are the values i am talking about.

I’ve tried several different things to fix this problem, however nothing i’ve done has worked, so i’m figuring i am just missing something very simple that is causing this problem.

any help or suggestions are greatly appreciated. Thank you.

Answer 1

TO_TIMESTAMP_TZ expects a VARCHAR2 for its first parameter; you are passing it a DATE. Therefore, behind the scenes, Oracle is doing an implicit TO_CHAR conversion on your DATE that is causing you to lose precision in it, to the extent that the two originally different values are made the same.

Try first surrounding your DATE with a TO_CHAR supplied with an explicit format, then pass that to TO_TIMESTAMP_TZ. Something like:

SQL> VAR startoffset NUMBER
SQL> VAR endoffset   NUMBER
SQL> EXEC :startoffset := 4260; :endoffset := 4740;

PL/SQL procedure successfully completed.

SQL> SELECT TO_TIMESTAMP_TZ(TO_CHAR((TO_DATE('3/13/2012 7:00 PM'
  2                                  ,       'MM/DD/YYYY HH:MI AM')
  3                               - (3300  / 24 / 60))
  4                               + (:startoffset / 24 / 60)
  5                         ,        'YYYY-MM-DD HH24:MI:SS')
  6         ,               'YYYY-MM-DD HH24:MI:SS TZH:TZM')    AS shift_start_date
  7  ,      TO_TIMESTAMP_TZ(TO_CHAR((TO_DATE('3/14/2012 1:00 AM'
  8                                  ,       'MM/DD/YYYY HH:MI AM')
  9                               - (5220 / 24 / 60))
 10                               + (:endoffset   / 24 / 60)
 11                         ,        'YYYY-MM-DD HH24:MI:SS')
 12         ,               'YYYY-MM-DD HH24:MI:SS TZH:TZM')    AS shift_end_date
 13  FROM DUAL;

SHIFT_START_DATE                                                            SHIFT_END_DATE
--------------------------------------------------------------------------- ---------------------------------------------------------------------------
14-MAR-12 11.00.00.000000000 AM -05:00                                      13-MAR-12 05.00.00.000000000 PM -05:00

SQL>

Hope this helps.