Postgres example distinct

postgres_example_distinct.sql

WITH cohorts_join AS (SELECT 
  cohorts.id, 
  cohorts.name, 
  cohorts.settings, 
  cohorts.created_at, 
  cohorts.updated_at, 
  registrations.product_id, 
  products.type AS product_type
FROM cohorts, cohorts_registrations, registrations, products 
WHERE 
  cohorts.id = cohorts_registrations.cohort_id
  AND cohorts_registrations.registration_id = registrations.id 
  AND registrations.product_id = products.id
)
SELECT DISTINCT ON (id, product_id) * FROM cohorts_join;