There are two issues.
when data stored in table that date format is dd-mm-rr.
This is completely wrong. Oracle doesn't store the date in the format you see, what you see is for display. Oracle stores DATE in an internal proprietary format in 7 bytes
with each byte representing different elements of the DATE.
Byte Description
---- -------------------------------------------------
1 Century value but before storing it add 100 to it
2 Year and 100 is added to it before storing
3 Month
4 Day of the month
5 Hours but add 1 before storing it
6 Minutes but add 1 before storing it
7 Seconds but add 1 before storing it
Do not depend on the locale_specific NLS_DATE_FORMAT. Always use:
- TO_CHAR to display the date in your desired format
- TO_DATE to explicitly convert the string into date.
Remember, TO_DATE is NLS dependent.
If you only have a date element, and if you do not care about the time element, then better use ANSI Date literal which follows a fixed format 'YYYY-MM-DD'
.
only month display in junk characters
This is again because you are depending on the NLS_DATE_LANGUAGE. As I said, you should avoid depending on the locale-specific client settings. Explicitly mention the NLS_DATE_LANGUAGE
or use ANSI Date literal if you are not concerned about the time element.
For example,
SQL> SELECT TO_CHAR(SYSDATE, 'DD-MON-RR') dt FROM DUAL;
DT
---------
26-OCT-15
SQL> alter session set nls_date_language='french';
Session altered.
SQL> SELECT TO_CHAR(SYSDATE, 'DD-MON-RR') dt FROM DUAL;
DT
-----------
26-OCT. -15
So, what happened above? for a person using FRENCH nls_date_language
, the MONTH is showing junk value. Let's make it NLS independent by explicitly mentioning the nls_date_language
.
SQL> SELECT TO_CHAR(SYSDATE, 'DD-MON-RR', 'nls_date_language=english') dt FROM DUAL;
DT
---------
26-OCT-15
Also, the NLS_LANG value might not be correctly set in the OS environmental variable. See Why are junk values/special characters/question marks displayed on my client?