Oracle 18c

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select replace (replace (replace ('abc', 
    'a', 'd'), 
    'b', 'e'),
    'c', 'f') result
from dual


RESULT


def


create table params (id, key, val) as 
    select 1, 'a', 'd' from dual union all
    select 2, 'b', 'e' from dual union all
    select 3, 'c', 'f' from dual
3 rows affected

create or replace type kvarg is object (key varchar2 (32), val varchar2 (32))
/
create or replace type kvargs is table of kvarg
/
with 
function replaceall (str varchar2, kv kvargs) return varchar2 is
    ret varchar2 (32767) := str;
begin
    for i in 1..kv.count loop
        ret := replace (ret, kv(i).key, kv(i).val); 
    end loop;
    return ret;
end;
param (args) as (
    select cast (multiset (
        select key, val 
        from params order by id) as kvargs) 
    from dual
)
select replaceall ('abc', args) result
from dual, param
/


RESULT


def