SQL date query problem with century/ year

Question

We have an oracle database with about 6 million records. There is a date field called Entered Date that ranges from 1985 to the present.
The majority of these records were entered prior to Jan 1 2000.
If I run a query like
select count(*) from (tablename) where entered_date < '01-JAN-00' I get 0
if I do
select count(*) from (tablename) where entered_date < '31-DEC-99' I get 0
BUT IF I DO
select count(*) from (tablename) where entered_date < '01-JAN-00' I get 6 million records
or
select count(*) from TREASURY.ctrc where entrydate > '31-DEC-99' I get 6 million records
I've tried the same queries using 4 digit years but get the same results; it thinks that 2000 is the less than 1999
How do I get around this?
thanks

Answer 1

Hi,
975204 wrote:
there are 6 million records on the table
about two thirds have a date prior to Jan 1 , 2000How do you know that? From knowledge of the application, you may know that two thirds of them are supposed to have dates prior to 2000, but if
SELECT  COUNT (*)
FROM      TABLE_NAME
WHERE      ENTRYDATE < TO_DATE ( '01-JAN-2000'
                       , 'DD-MON-YYYY'
;returns 0, that's pretty strong proof that none of them actually do.
When I look at the dates , they display as 31-DEC-86Another example of why using 2-digit years is such a bad idea.
I cant actually provide dump of this clients confidential dataSeriously; you can't provide one DUMP output? You've already said that it displays as 31-DEC-86, so even if the fact that 1 entry in the 6-million row table was done on December 31, 1986 was such a big secret, it's already out, and you won't be causing any more harm by showing the DUMP results.
I ran the query with the same format as the date ie
SELECT COUNT(*) FROM TREASURY.CTRC WHERE ENTRYDATE < TO_DATE ( '31-DEC-99'
, 'DD-MON-YY'
but same results
if the column is defined as a DATE type, does Oracle make a distinction based on how the data displays, meaning does it think that 31-DEC-86 is different than 31-DEC-1986?No, all DATE columns have the same format. A DATE may be displayed one way of the other, but it is stored as neither.
Do I need to convert all the data to a 4 digit year? You should always display dates with a 4-digit year.
Run an update query that says if year >= 80 and <= 99 add 19 in front of the year, else add 20 in front of the yearLet's find out exactly what the problem is, first.
Did you see Ascheffer's message? ^1^ It was dated just a couple of minutes before your last message, so you might not have noticed it. Run it to see what the actual 4-digit years are.
If it shows, for example, that there are a lot of entrydates in the years 2080 to 2099, and you decide that all of those really should be 100 years earlier, then use ADD_MONTHS to correct them:
UPDATE     table_name
SET     entrydate = ADD_MONTHS ( entrydate
                           , -100 * 12
WHERE   entrydate >= TO_DATE ( '01-JAN-2080'
                         , 'DD-MON-YYYY'
AND     entrydate <  TO_DATE ( '01-JAN-2100'
                         , 'DD-MON-YYYY'
;Edited by: Frank Kulash on Mar 15, 2013 6:09 PM
^1^ Obviously, you did see Ascheffer's message; I was still typing the message above when you posted another one.