[HR] Olivander's Inventory*

• Basic Join > multiple join key
  https://www.hackerrank.com/challenges/harry-potter-and-wands/problem?isFullScreen=true

select w.id
      ,wp.age
      ,w.coins_needed
      ,w.power
from wands w
inner join wands_property wp
on w.code = wp.code
inner join (
    select wp1.age
          ,w1.power
          ,min(w1.coins_needed) min_coins_needed
    from wands w1
    inner join wands_property wp1
    on w1.code = wp1.code 
    where 1=1
    and wp1.is_evil = 0
    group by wp1.age, w1.power) m
on wp.age = m.age
and w.power = m.power
and w.coins_needed = m.min_coins_needed
order by w.power desc, wp.age desc