SQL> SELECT
  2    LENGTH('sushanthsharma') - LENGTH(REPLACE('sushanthsharma', 's', '')) l
  3  FROM dual;

               L
----------------
               3

SQL>

SQL> SELECT SUM(DECODE(SUBSTR('sushanthsharma', LEVEL, 1), 's', 1, 0)) cnt
  2  FROM dual
  3  CONNECT BY LEVEL <= LENGTH('sushanthsharma');

             CNT
----------------
               3

SQL>

SQL> SELECT COUNT(DISTINCT INSTR('sushanthsharma', 's', LEVEL)) cnt
  2  FROM dual
  3  WHERE INSTR('sushanthsharma', 's', LEVEL) <> 0
  4  CONNECT BY LEVEL <= LENGTH('sushanthsharma');

             CNT
----------------
               3

SQL>

SQL> SELECT LENGTH(REGEXP_REPLACE(TRANSLATE('sushanthsharma',
  2                                         'abcdefghijklmnopqrstuvwxyz',
  3                                         '                  *       '
  4                                        ), '[[:blank:]]+', ''
  5                              )) cnt
  6  FROM dual;

             CNT
----------------
               3

SQL>