Replace the spacial character in the string....

select 'Elangovan,Ragavan' from dual

select REPLACE('Elangovan,Ragavan',',',' ') test1 from dual

Replace 'cde' to 'XXX'

select 'abcdefghicde' from dual

SELECT REPLACE('abcdefghicde','cde','xxx') from Dual;

SUBSTR And INSTR 

select SUBSTR('Elangovan',1,1) from dual

select SUBSTR('Elangova,n',1,instr('Elangova,n,ra',',',1,1)-1) from dual