list = sort([p1, p2, p3, p4]);

m1 = makestring(list[0], ":", list[1]);
m2 = makestring(list[0], ":", list[1], ":", list[2]);
m3 = makestring(list[0], ":", list[1], ":", list[2], ":", list[3]);

select id
    , (select id from nodes a where a.m1 = t.m1 && a.id != t.id limit 1) c1
    , (select id from nodes b where b.m2 = t.m2 && a.id != t.id limit 1) c2
    , (select id from nodes c where c.m3 = t.m3 && a.id != t.id limit 1) c3
from nodes t

create table nodes 
(
   id int
   , p1 int
   , p2 int
   , p3 int
   , p4 int
   , m1 char(15), key _m1 (m1)
   , m2 char(15), key _m2 (m2)
   , m3 char(15), key _m3 (m3)
)
engine = innodb
character set utf8
collate utf8_general_ci;