Date issue stopping export program.

Question

Hi All,
We are using Oracle 11g version.
We are exporting the data from the DB to a .txt file. If the next run date of the report in a status table is greater than or equal to system date then export should happen.
--Note: <Report Name> is the in param.
Execute immediate 'ALTER SESSION SET NLS_DATE_FORMAT =''DD-MON-RR''';
COMMIT;
FOR i IN (Select reportid from status_table where reportname = <Report Name> and status = 'SCHEDULED' and *NextRunDate <= SYSDATE*)
LOOP
  l_query := l_QueryFromTable;
Select (NextRunDate) into lv_NextRunDate from status_table where reportname = <Report Name> and status IN ('SCHEDULED');
Execute immediate 'ALTER SESSION SET NLS_DATE_FORMAT =''MM/DD/YYYY HH24:MI:SS''';
COMMIT;
-- Then start the export program......
End Loop;The above code was working perfectly fine but it stopped working suddenly. I added TRUNC while selecting from table and comparing dates. It is working now.
Now, Question is;
How come the code stopped working which was working fine before? Is it happening because "nls_date_params" being altered?
Is TRUNC solution resolves my issue permanently?
Please let me know.
Thanks and Regards
Nagaraja Akkivalli.

Answer 1

Thanks WhiteHat for the response.
Yes, you are right. Cursor was not returning any data. Due to which, export stopped working.
Normal comparision of the dates does not consider timestamp due to which we started altering nls_date_parameters.
For example,
We load files to transactionl tables. If the files loads @ 12:59:53 then we check the tables recors for this file as below.
(TrxnTable.EntryCreatedDate) between  '12-DEC-2011' and '12-DEC-2011' does not returns the correct results.
However, below two queries returns the proper results.
(TrxnTable.EntryCreatedDate) between  '12-DEC-2011 00:00:00' and '12-DEC-2011 23:59:59'
or
trunc(TrxnTable.EntryCreatedDate) between  '12-DEC-2011' and '12-DEC-2011' Also, Many times we perform some operations on timestamp. That is why we are altering nls_date_parameters.
Note: Defaults nls date param is 'DD-MON-RR'. Export program starts @ 6:00:00 AM.
Table structure and data FYI.
CREATE TABLE STATUS_TABLE
     REPORTID  NUMBER(20,0),
      REPORTNAME  VARCHAR2(100 BYTE),
      NEXTRUNDATE  DATE,
      CREATED_DATE  DATE,
      CONSTRAINT  STATUS_TABLE_PK  PRIMARY KEY ( REPORTID )  
ReportID     Report Name     NextRun Date
7503          ReportX          12/12/2011 8:01
7502          ReportY          12/11/2011 8:01
7491          RepiotZ          12/10/2011 8:01
7490          ReportX          12/9/2011 8:01
7489          ReportY          12/8/2011 8:01
7488          RepiotZ          12/7/2011 8:01Hope this infomation suffices to explain why export program stopped working.
Please let me know if you need any details.
Regards
Nagaraja.