sql function for checking if two persons have common ancestors - sql

Question

I have to solve the following problem: create a sql function that check if two persons have common ancestors, but I'm stuck.
I create
create type person as object
(
first_name varchar2(10),
last_namevarchar2(10)
);
and Persons table
create table client_iulia
(Person_Id varchar2(13)constraint pk_id_client primary key,
Mother_Id varchar2(13),
Father_Id varchar2(13),
Name person);
What I am trying to do is a function with three parameters (two people and search level) to return 1 if there are common ancestors and 0 otherwise)
Please, if anyone has any idea, help me.
Sorry for my poor english.

Answer 1

Recursive CTE is the way to go. I think it is the easiest to understand. There may be faster ways, but this should be clear how it works. I don't have access to an oracle server so I might have typos, I show two steps below so you can test and understand how it works.
1) Find all ancestors for a single input
with ancestors as
(
SELECT *
FROM client_iulia
WHERE Person_Id = #inputPerson
UNION ALL
SELECT *
FROM client_iulia
JOIN ancestors a on Person_ID = a.Mother_ID OR Person_ID = a.Father_ID
)
SELECT *
FROM ancestors
2) Find all ancestors for two targets
with ancestorsA as
(
SELECT *
FROM client_iulia
WHERE Person_Id = #inputPersonA
UNION ALL
SELECT *
FROM client_iulia
JOIN ancestorsA a on Person_ID = a.Mother_ID OR Person_ID = a.Father_ID
), ancestorsB as
(
SELECT *
FROM client_iulia
WHERE Person_Id = #inputPersonB
UNION ALL
SELECT *
FROM client_iulia
JOIN ancestorsB a on Person_ID = a.Mother_ID OR Person_ID = a.Father_ID
)
SELECT A.*
FROM ancestorsA A
JOIN ancestorsB B ON A.Person_Id = B.Person_Id

Answer 2

Wow, that's tricky. You need recursive queries to get all ancestors of either persons. As there are two parents, you will get pairs of mother and father, however, which you need to split into single ancestors. Then look if the sets have at least one ancestor in common. This statement gives you 1 when there is at least one common ancestor, else 0:
with ancestors_of_person_1 as
(
select mother_id, father_id
from client_iulia
start with person_id = 1
connect by person_id = prior mother_id or person_id = prior father_id
)
, ancestors_of_person_2 as
(
select mother_id, father_id
from client_iulia
start with person_id = 2
connect by person_id = prior mother_id or person_id = prior father_id
)
select count(*)
from
(
(
select mother_id as ancestor from ancestors_of_person_1
union
select father_id as ancestor from ancestors_of_person_1
)
intersect
(
select mother_id as ancestor from ancestors_of_person_2
union
select father_id as ancestor from ancestors_of_person_2
)
)
where rownum = 1;
EDIT: Here is an sqlfiddle. Person 1 and 3 have ancestor 122 in common, whereas person 1 and 2 have none in common. Try it: sqlfiddle