The below query can remove the consecutive duplicates. (to remove duplicates from comma separated list)
select regexp_replace('A,A,B,A','([^,]+)(,\1)*(,|$)', '\1\3') from dual
Result is A,B,A.
can i remove all the duplicates with regexp_replace from a string i.e .
source string = A,A,B,C,C,A,A,C Result should be = A,B,C