Puede ser que hayas hecho algo mal con la creación de expresiones regulares:hay un breve ejemplo.
-- create table:
create table tmp_a as
select unistr('\D841\DF0E') col from dual;
insert into tmp_a(col)
values(UNISTR('\D800\DC00'));
insert into tmp_a(col)
values(UNISTR('\D800\DC01'));
insert into tmp_a(col)
values(UNISTR('\D803\DC03'));
insert into tmp_a(col)
values(UNISTR('\041f'));
insert into tmp_a(col)
values('a');
insert into tmp_a(col)
values('b');
-- then check. There is should be 7 rows and only 4 should pass then "check"
select col, dump(col) , regexp_instr(col, '['||UNISTR('\F090\8080')||'-'||UNISTR('\F48F\BFBF')||']') as check from tmp_a ;
-- finaly we could build next query with regexp_like as in your example
select count(*)
from tmp_a
where regexp_like(col, '['||UNISTR('\F090\8080')||'-'||UNISTR('\F48F\BFBF')||']')
Funciona en Oracle 11.2.0.4 y 12.2.0.1
