outer.sql

ct_id(+) = c.contact_id; 

/*  It doesn't matter left or right side of the '=' sign. */
select P.P , C.C1, C.C2
from P,C
where C.C1(+) = P.P; 

select P.P , C.C1, C.C2
from P,C
where P.P = C.C1(+);