Trunc date fonction for last year

Question

hi all,
how can I get the first of each month of last year,
OK, I explain more,
I have a live database and a datawarhose and I need to purge all data of the month before actual month but of last year for the live DB.
exp:
the sysdate is *2010/12/09* and I should delete all record of table X between *2009/11/01* and *2009/12/01*
how can I use the trunc fonction to do this automaticly
thx a lot for your help, and excuse me for my english
Edited by: 809634 on Dec 9, 2010 11:22 AM

Answer 1

Hi,
To use John's idea in a DELETE statement:
DELETE     table_x
WHERE     dt_col     >= TRUNC (ADD_MONTHS (SYSDATE, -13), 'MONTH')
AND     dt_col     <  TRUNC (ADD_MONTHS (SYSDATE, -12), 'MONTH')
;where dt_col is the DATE column that decides if the row is too old to keep or not.
Do you really need the first condition? What if today is December 9, 2010, and, for some reason, there is still data in table_x from October 2009 as well as Novmber 2009? The statement above would leave all the rows from October 2009, but the following statement:
DELETE     table_x
WHERE     dt_col     <  TRUNC (ADD_MONTHS (SYSDATE, -12), 'MONTH')
;would leave only rows from December, 2009 or later.