Is there a way to format the way dates are displayed?

Question

ive got a query that returns dates. Currently, the code is:
SELECT uptd.delivery_month delivery_time
FROM USER_pwr_term_data uptd
WHERE uptd.eff_date='07/JUN/02'
the data in the database is listed in the format of 07/01/2002 and cannot be changed.
the output from the query is coming out as 2002-07-01 0:00:00
i am looking for the output date to be simply Jul-02 or something to this effect.
Thanks,
Jared

Answer 1

In the group by and order by clauses, you need to use whatever to_char format that you want to group by and order by. For example, if you want to order by the year, then the numerical month, then use to_char and 'YYYY-MM'.
If you want to display the column in the select clause in a different format than what you group by and order by, then you need to wrap an additional to_date around the format that you used for group by and order by, to convert it back to a date format, and another to_char around that, to convert it to the format you want to display it in. For example, if you want to display it like Jul-02, where 02 represents the year 2002, then use to_char and 'Mon-YY', wrapped around the to_date, wrapped around the format you used in the group by and order by clauses.
Please see the example below. Also, notice that how the date is displayed by default, is dependent upon the nls_date_format. Also, notice that every value of eff_date that I entered is the same, despite the fact that I entered it in various formats, because I used to_date.
SQL> ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD'
  2  /
Session altered.
SQL> SELECT SYSDATE FROM DUAL
  2  /
SYSDATE
2002-06-24
SQL> CREATE TABLE user_pwr_term_data
  2    (delivery_month DATE,
  3     eff_date       DATE)
  4  /
Table created.
SQL> INSERT INTO user_pwr_term_data
  2  VALUES (SYSDATE, TO_DATE ('06/07/2002', 'MM/DD/YYYY'))
  3  /
1 row created.
SQL> INSERT INTO user_pwr_term_data
  2  VALUES (SYSDATE + 30, TO_DATE ('07/JUN/2002', 'DD/MON/YYYY'))
  3  /
1 row created.
SQL> INSERT INTO user_pwr_term_data
  2  VALUES (SYSDATE - 30, TO_DATE ('07/Jun/2002', 'DD/Mon/YYYY'))
  3  /
1 row created.
SQL> INSERT INTO user_pwr_term_data
  2  VALUES (SYSDATE + 31, TO_DATE ('06/07/2002', 'MM/DD/YYYY'))
  3  /
1 row created.
SQL> INSERT INTO user_pwr_term_data
  2  VALUES (SYSDATE - 31, TO_DATE ('06/07/2002', 'MM/DD/YYYY'))
  3  /
1 row created.
SQL> COMMIT
  2  /
Commit complete.
SQL> SELECT * FROM user_pwr_term_data
  2  /
DELIVERY_M EFF_DATE
2002-06-24 2002-06-07
2002-07-24 2002-06-07
2002-05-25 2002-06-07
2002-07-25 2002-06-07
2002-05-24 2002-06-07
SQL> SELECT      TO_CHAR (TO_DATE
  2                  (TO_CHAR (uptd.delivery_month, 'YYYY-MM'),
  3                'YYYY-MM'), 'Mon-YY') AS delivery_time,
  4              COUNT (*) AS total -- or other group function
  5  FROM        user_pwr_term_data uptd
  6  WHERE       uptd.eff_date = TO_DATE ('07/JUN/2002', 'DD/MON/YYYY')
  7  GROUP BY TO_CHAR (uptd.delivery_month, 'YYYY-MM')
  8  ORDER BY TO_CHAR (uptd.delivery_month, 'YYYY-MM')
  9  /
DELIVE      TOTAL
May-02          2
Jun-02          1
Jul-02          2