How do I remove case-sensitive settings from Oracle?! __oracle

When querying the data,

SQL Server is not case-sensitive by default. If you want to differentiate, you need additional settings.

Oracle is case sensitive by default. If you don't differentiate, you need additional settings.

The following are the scripting settings that are not differentiated:
ALTER session SET Nls_comp=ansi;
ALTER session SET Nls_sort=binary_ci;

But this is in the current session, that is, every time you initiate a query, you need to do this to work.

But there are other theories on the web that are dealt with in the following ways:

SELECT * from TUSER where Lower (user_code) = ' Billy ' 
or 
select * from TUSER where upper (User_code) = ' Billy ' 

But this approach can lead to two problems:

1, the use of lower or upper will not be able to use the index.
2, the proposed data in the time you should be data format.