SQL & PL/SQL :: Join Condition - One Column Vs Many?

create table ptab(pid number);
create table ctab(aphone varchar2(20));
drop table ctable
create table xtab(pid number,phone varchar2(20), tel1 varchar2(20), tel2 varchar2(20), tel3 varchar2(20))

insert into ptab values(1);
insert into ptab values(2);
insert into ptab values(3);
insert into ptab values(4);

[code]..

i have 3 tables, xtab, ctab and ptab

join condition

ptab.pid = xtab.pid
and
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what I want the join between xtab and ctab is, aphone should match with phone, and then tel1, then tel2, and then tel3, (if phone, tel1, tel2, tel3 are not null in that order only), if aphone matches with any of these,then just print that particular pid, important point is, aphone should be checked against phone, tel1, tel2, tel3 that order only

so the results should simply print

pid
1
2
3
4
5 should not be printed here because for pid 5 in xtab, none of the phone numbers match with aphone of ctab

I tried this:
select
DECODE (ctab.aphone,
xtab.phone, 1,
xtab.tel1, 1,
xtab.tel2, 1,

[code]...

but i cannot join ctab and ptab, i dont want to use intersect etc, because we are looking at millions of rows here