Sql statement not showing right result set

Question

Hi everyone,
I have a statement :
select to_date(extract (day from to_date(begin_datum,'yyyy-mm-dd'))||'-'||extract (month from to_date(begin_datum,'yyyy-mm-dd'))||'-'||
extract(year from sysdate),'dd-mm-yyyy') from fus_medewerkers;
which returns following result:
12-FEB-09
07-DEC-09
22-NOV-09
21-MAY-09
26-FEB-09
17-DEC-09
01-SEP-09
17-DEC-09
04-APR-09
07-JUN-09
23-MAY-09
29-MAY-09
13-AUG-09
18-MAR-09
01-NOV-09
12-AUG-09
06-JAN-09
01-MAR-09
02-AUG-09
16-AUG-09
06-NOV-09
23-MAR-09
06-MAY-09
01-NOV-09
01-MAR-09
16-AUG-09
01-JAN-09
01-DEC-09
01-OCT-09
01-OCT-09
01-OCT-09
01-APR-09
01-APR-09
08-DEC-09
01-APR-09
01-AUG-09
14-JUN-09
02-JUL-09
01-APR-09
10-JAN-09
15-MAR-09
07-APR-09
29-JAN-09
16-JUN-09
21-OCT-09
I now put a condition in my original statement as follow:
select to_date(extract (day from to_date(begin_datum,'yyyy-mm-dd'))||'-'||extract (month from to_date(begin_datum,'yyyy-mm-dd'))||'-'||
extract(year from sysdate),'dd-mm-yyyy') from fus_medewerkers
where sysdate <= to_date(extract (day from to_date(begin_datum,'yyyy-mm-dd'))||'-'||extract (month from to_date(begin_datum,'yyyy-mm-dd'))||'-'||
extract(year from sysdate),'dd-mm-yyyy');
The result is:
07-DEC-09
22-NOV-09
17-DEC-09
01-SEP-09
17-DEC-09
13-AUG-09
01-NOV-09
16-AUG-09
06-NOV-09
01-NOV-09
16-AUG-09
01-DEC-09
01-OCT-09
01-OCT-09
01-OCT-09
08-DEC-09
21-OCT-09
As you can see the row with sysdate (12-AUG-09 ) in my first result is not shown in the second result set.
Can someone please tell me why this is so and how I could solve this problem?
Regards,
Diana

Answer 1

sysdate contains time even if it's not shown. e.g. at 14:43:22 on Aug 12th 2009, sysdate would have a value of 12-AUG 2009 14:43:22, but unless you have changed your NLS_DATE_FORMAT setting you would only see the date portion of it.
When comparing a date value to sysdate you may need to truncate one or both values depending on the results you are looking for.
e.g.
the only difference between these two queries is that I truncate sysdate in one of them:
with t1 as (select 1 id, to_date('12-AUG-2009','dd-mon-yyyy') dt from dual
  union all select 2, to_date('12-AUG-2009 14:23','dd-mon-yyyy hh24:mi') from dual
select sysdate, t1.* from t1 where sysdate <= dt
SYSDATE                   ID                     DT                       
12-AUG-2009 11:38:21      2                      12-AUG-2009 14:23:00     
1 rows selected
with t1 as (select 1 id, to_date('12-AUG-2009','dd-mon-yyyy') dt from dual
  union all select 2, to_date('12-AUG-2009 14:23','dd-mon-yyyy hh24:mi') from dual
select trunc(sysdate), t1.* from t1 where trunc(sysdate) <= dt
TRUNC(SYSDATE)            ID                     DT                       
12-AUG-2009 00:00:00      1                      12-AUG-2009 00:00:00     
12-AUG-2009 00:00:00      2                      12-AUG-2009 14:23:00     
2 rows selected