SELECT * FROM TABLE_NAME 
WHERE 
LENGTH(REPLACE(TRANSLATE(str,'asdfghjklqwertyuiopzxcvbnm1234567890','                                   '),' ',''))>0

SQL> select * from special_char;

SCHAR
-------
abc$
abc
13489
kos*
289#


SQL> select * from special_char
  2  where regexp_like(schar,'[^[:alnum:]]');

SCHAR
---------
abc$
kos*
289#

drop table fe_special_characters;

create table fe_special_characters
   (
   why char(1),
   ascii_code number(3)
   );

DECLARE

   strPokerAlias ods.tbl_crypto_accounts.username%TYPE;
   i int;
   strWhy char(1) := 'X';
   strMaster varchar2(100);

   /* Cursor declaration: */

   CURSOR T1Cursor IS

   SELECT 
      ods.tbl_crypto_accounts.username
   FROM
      ods.tbl_crypto_accounts
   WHERE
      username is not null and
      REGEXP_INSTR(username,'[^a-z^A-Z^0-9]') > 0;

   BEGIN

   OPEN T1Cursor;

   LOOP

      FETCH T1Cursor INTO strPokerAlias;

      EXIT WHEN T1Cursor%NOTFOUND;

           FOR i in 1..length(strPokerAlias) LOOP
   
               strWhy := substr(strPokerAlias,i,1);
               
               IF REGEXP_INSTR(strWhy,'[^a-z^A-Z^0-9]') > 0 
               
               THEN 
                                                
                  IF nvl(instr(strMaster,strWhy,1,1),0) = 0
               
                  THEN strMaster := strMaster||strWhy;
                  
                  insert into fe_special_characters values(strWhy,ascii(strWhy));
                     
                  END IF;
                  
               END IF;
               
           END LOOP;

      commit;
            
      END LOOP;

      CLOSE T1Cursor;

   END;
/   

select * from fe_special_characters;