With several third-party databases, it is common for queries to be case insensitive. For example, in such cases the following queries return the same results:
SELECT * FROM orders WHERE sales_rep = 'Oracle';
SELECT * FROM orders WHERE sales_rep = 'oracle';
SELECT * FROM orders WHERE sales_rep = 'OrAcLe';
If you want queries to be case insensitive for a user in the Oracle database, you can create an AFTER LOGON ON DATABASE trigger, in which you set, for that database user, the NLS_SORT session parameter to an Oracle sort name with _CI (for "case insensitive") appended.
The following example causes queries for user SMITH to use the German sort order and to be case insensitive:
CREATE OR REPLACE TRIGGER set_sort_order AFTER LOGON ON DATABASE
DECLARE
username VARCHAR2(30);
BEGIN
username:=SYS_CONTEXT('USERENV','SESSION_USER');
IF username LIKE 'SMITH' then
execute immediate 'alter session set NLS_COMP=LINGUISTIC';
execute immediate 'alter session set NLS_SORT=GERMAN_CI';
END IF;
END;
Source : oracle help
