Return row only if value doesn't exist

Question

I have 2 tables - reservation:

   id  | some_other_column
   ----+------------------
   1   | value
   2   | value
   3   | value

Answer 1

Just for completeness (and I honestly believe it fits better), I encourage you to use a simple NOT EXISTS.

SELECT * FROM reservation R
WHERE NOT EXISTS (
  SELECT 1 FROM reservation_log
  WHERE reservation_id = R.id
    AND change_type = 'cancel'
);