Why is "?" Displayed in lowercase "i"? after executing NLS_UPPER

Capital i

in Turkish İ

(U + 0130: latin letter i with dot above), see https://codepoints.net/U+0130

The Turkish alphabet, which is a variant of the Latin alphabet, includes two different versions of the letter I, one dotted and the others countless.

Infinite I, I ı, denotes a closed reverse unbaked vowel sound (/ Ɯ /). Neither the top nor the bottom version has a dot.

Dotted I, İ i, denotes a close front without a circular vowel (/ i /). Both upper and lower case variants have a period.

Examples:

• İstanbul / istanbuɫ / (starts with the sound i, not ı).

• Diyarbakır / dijaɾbakɯɾ / (the first and last vowels are written and pronounced differently)

It looks like your database character set does not support this character, what is your database character set? Check with

SELECT * 
FROM V$NLS_PARAMETERS 
WHERE PARAMETER IN ('NLS_CHARACTERSET', 'NLS_NCHAR_CHARACTERSET');

      

        
        
        
      

    

I guess

DBMS_OUTPUT.PUT_LINE('NLS_UPPER(abcdefghijklmnopqrstuvwxyz) = '
   || NLS_UPPER(N'abcdefghijklmnopqrstuvwxyz')); 

      

        
        
        
      

    

must work.

You must set your NLS_LANG

and console encoding correctly for correct output. Here are some working examples:

C:\>set NLS_LANG=.AL32UTF8
C:\>chcp 65001
Active code page: 65001

C:\>sqlplus ...
select nls_upper('i', 'nls_sort = xturkish') from dual;



C:\>set NLS_LANG=.TR8MSWIN1254
C:\>chcp 1254
Active code page: 1254

C:\>sqlplus ...
select nls_upper('i', 'nls_sort = xturkish') from dual;




C:\>set NLS_LANG=.SE8ISO8859P3
C:\>chcp 28593
Active code page: 28593

C:\>sqlplus ...
select nls_upper('i', 'nls_sort = xturkish') from dual;




C:\>set NLS_LANG=.WE8ISO8859P9
C:\>chcp 28599
Active code page: 28599

C:\>sqlplus ...
select nls_upper('i', 'nls_sort = xturkish') from dual;