select w.id, wp.age, w.coins_needed, w.power from
wands w inner join (
    select code, power, min(coins_needed) as min_coins from wands
    group by code, power) as mc
    on w.code = mc.code
inner join wands_property wp on w.code = wp.code
where wp.is_evil = 0
and
w.coins_needed = mc.min_coins
order by mc.power desc, wp.age desc