Help ! for date column type

Question

Hi,
I am having two tables tdz12 and tdf31. TDF31 is a date field. and TDZ12 is transactions history table. If I do
11:30:39 SQL> alter session set nls_date_format='DD-MON-RRRR HH24:MI:SS';
11:30:57 SQL> select c65201 from tdf31;
C65201
30-NOV-2006 00:00:00
11:46:48 SQL> select distinct a9000 from tdz12 where a9000 >= '01-NOV-06';
A9000
01-NOV-2006 00:00:00
02-NOV-2006 00:00:00
03-NOV-2006 00:00:00
04-NOV-2006 00:00:00
06-NOV-2006 00:00:00
07-NOV-2006 00:00:00
08-NOV-2006 00:00:00
09-NOV-2006 00:00:00
10-NOV-2006 00:00:00
11-NOV-2006 00:00:00
13-NOV-2006 00:00:00
14-NOV-2006 00:00:00
15-NOV-2006 00:00:00
16-NOV-2006 00:00:00
17-NOV-2006 00:00:00
18-NOV-2006 00:00:00
20-NOV-2006 00:00:00
21-NOV-2006 00:00:00
22-NOV-2006 00:00:00
23-NOV-2006 00:00:00
24-NOV-2006 00:00:00
25-NOV-2006 00:00:00
27-NOV-2006 00:00:00
28-NOV-2006 00:00:00
29-NOV-2006 00:00:00
30-NOV-2006 00:00:00
26 rows selected.
If I do
11:26:39 SQL> select sum(a9060)
11:27:52 2 from tdz12
11:27:52 3 where A9000>=(select to_date(to_char(C65201,'YYYYMM')||'01','YYYYMMDD') FROM TDF31);
SUM(A9060)
0
Why I am getting 0 records ? ( Pl tell me the reason, not alternate way to get records )
thanks & regards
PJP

Answer 1

TRUNC(c65201,'MONTH')is a simpler alternative to
TO_DATE(TO_CHAR(c65201,'YYYYMM')||'01','YYYYMMDD')although it will give the same result here.