Change date precision values

As a_horse indicated, select min(date)... is sufficient. The DECODE and multiple conversions just slow things down without accomplishing anything. Even as parts of queries, you should eliminate this needless processing.

As Phil indicated, the displaying of dates is controlled by the NLS_DATE_FORMAT parameter and can be altered to display dates as you wish. This does change how the queries run (unless there are missing format specifications or SQL injection is being done). Change the display format like this:

 ALTER SESSION SET NLS_DATE_FORMAT='YYYYMMDD';

When doing a to_date on a two digit year, use YY when you want the first two digits of the year to match the current year, but use RR when you want the first two digits to be 20 for years ending in 0-49 and 19 for years ending in 50-99. See the SQL Language Reference for more information:

The RR datetime format element is similar to the YY datetime format element, but it provides additional flexibility for storing date values in other centuries. The RR datetime format element lets you store 20th century dates in the 21st century by specifying only the last two digits of the year.

If you use the TO_DATE function with the YY datetime format element, then the year returned always has the same first 2 digits as the current year. If you use the RR datetime format element instead, then the century of the return value varies according to the specified two-digit year and the last two digits of the current year.

That is:

• If the specified two-digit year is 00 to 49, then

  • If the last two digits of the current year are 00 to 49, then the returned year has the same first two digits as the current year.

  • If the last two digits of the current year are 50 to 99, then the first 2 digits of the returned year are 1 greater than the first 2 digits of the current year.

• If the specified two-digit year is 50 to 99, then

  • If the last two digits of the current year are 00 to 49, then the first 2 digits of the returned year are 1 less than the first 2 digits of the current year.

  • If the last two digits of the current year are 50 to 99, then the returned year has the same first two digits as the current year.

The following examples demonstrate the behavior of the RR datetime format element.

SELECT TO_CHAR(TO_DATE('27-OCT-98', 'DD-MON-RR'), 'YYYY') "Year" FROM DUAL; 
Year
---- 
1998 

SELECT TO_CHAR(TO_DATE('27-OCT-17', 'DD-MON-RR'), 'YYYY') "Year" FROM DUAL; 
Year
----
2017

If I understand the problem correctly, when both users have British as default language, one user's request goes through fine because the language setting changes automatically to us_english. But for another user, the language setting doesn't change automatically, hence the error.

The BOL states following regarding default language and how it can be overridden.

The default language for a login can be overridden by using CREATE LOGIN or ALTER LOGIN. The default language for a session is the language for that session's login, unless overridden on a per-session basis by using the Open Database Connectivity (ODBC) or OLE DB APIs. Note that you can only set the default language option to a language ID defined in sys.syslanguages (0-32). When you are using contained databases, a default language can be set for a database by using CREATE DATABASE or ALTER DATABASE, and for contained database users by using CREATE USER or ALTER USER. Setting default languages in a contained database accepts langid value, the language name, or a language alias as listed in sys.syslanguages.

Based on this the following can affect the language setting.

• Database default
• User default
• DSN setting, connection strings, etc..
• SET LANGUAGE in session

If underlying statements can't be changed, is there a setting that can affect it in the third party app? Or is there are trigger for a certain user login? Though I believe it's one or a combination of 2 or more in the above list....