Question

I’m trying to get better performance out of this Oracle query (which is terribly slow). I’m an Oracle beginner so maybe someone can point out a better way to approach this query.

I have a table with information on different families. I want to extract the different relationships based on a relationship type. The solution I came up with uses a hash join to query the database…

select *
from (
  with target_person as (
    select 
      p.person_id,
      p.family_number,
      p.relationship_type_id
    from 
      people p
    where
      p.relationship_type_id = 1 -- parent
  )
  select
    target_person.person_id,
    related_person.related_person_id,
    related_person.relationship_type_id
  from
    target_person,
    people related_person
  where
    target_person.person_id != related_person.person_id
    and target_person.family_number = related_person.family_number
    and related_person.relationship_type_id = 1
);

Answer 1

You realize this is equivalent to this?:

select *
from (
  with target_person as (
    select 
      p.person_id,
      p.family_number,
      p.relationship_type_id
    from 
      people p
    where
      p.relationship_type_id = 1 -- parent
  )
  select
    target_person.person_id,
    related_person.related_person_id,
    related_person.relationship_type_id
  from
    target_person,
    target_person related_person
  where
    target_person.person_id != related_person.person_id
    and target_person.family_number = related_person.family_number
);

So it’s really as simple as this:

SELECT *
FROM people AS l
INNER JOIN people AS r
ON l.family_number = r.family_number
    AND l.relationship_type_id = 1
    AND r.relationship_type_id = 1
    AND l.person_id <> r.person_id

I would think the way to get this to go fastest is to have an index on relationship_type_id, family_number, person_id on your people table.