Selecting dates problem

Question

Hi all,
I'm having astrange problem while selecting dates. Could someone please tell me what's wrong:
I'm selecting from S_ASSET_CON, and ATTRIB_26 is the name of the problematic field:
desc S_ASSET_CON;
Name Null? Type
ATTRIB_26 DATE
The query:
SELECT
SAC.ATTRIB_26
FROM S_ASSET SA, S_ASSET_CON SAC, S_PROD_INT SPI
WHERE
SA.SERIAL_NUM = 'XXX'
AND SAC.ASSET_ID = SA.ROW_ID
AND SA.PROD_ID = SPI.ROW_ID;
gives:
ATTRIB_26
06-AUG-10
The query:
SELECT
SAC.ATTRIB_26
FROM S_ASSET SA, S_ASSET_CON SAC, S_PROD_INT SPI
WHERE
SA.SERIAL_NUM = 'XXX'
AND TO_CHAR(SAC.ATTRIB_26, 'YYYY-MM-DD') = '2010-08-06'
AND SAC.ASSET_ID = SA.ROW_ID
AND SA.PROD_ID = SPI.ROW_ID;
gives:
ATTRIB_26
06-AUG-10
But the query:
SELECT
SAC.ATTRIB_26
FROM S_ASSET SA, S_ASSET_CON SAC, S_PROD_INT SPI
WHERE
SA.SERIAL_NUM = 'XXX'
AND SAC.ATTRIB_26 = TO_DATE('2010-08-06', 'YYYY-MM-DD')
AND SAC.ASSET_ID = SA.ROW_ID
AND SA.PROD_ID = SPI.ROW_ID;
returns no row:
no rows selected
Why doesn't the 3rd query return anything??
Thank you in advance!
C

Answer 1

There are mainly 2 reasons
1) If u had inserted hard codedly like
SQL>insert into S_ASSET_CON values ('06-AUG-10');
thn it wud return u the output as it stores the same value
so when u compare S_ASSET_CON='06-AUG-10' thn it will dispalyed
where as if u insert using date format like
SQL>insert into S_ASSET_CON select sysdate from dual;
thn internally it will be stored in the format as 'DD-MON-YY HH24:MI:SS'
so the value of ATTRIB_26='06-AUG-10 13:14:15'
so whn u compare the value will not be matched and so it doesn't return any rows
2)ur 1st query output shows tht ur column has 'DD-MON-YY' date format
and in ur 3rd query
AND SAC.ATTRIB_26 = TO_DATE('2010-08-06', 'YYYY-MM-DD')
here SAC.ATTRIB_26 ,its datatype is date so by default the format will be 'DD-MON-YY' and ur comparing with the format as 'YYYY-MM-DD'
so its also one of the reasons for not returning the value
Regards,
Santosh Minupurey