如何避免对此mysql查询进行全表扫描？

explain
select
    *
from
    zipcode_distances z 
inner join
    venues v    
    on z.zipcode_to=v.zipcode
inner join
    events e
    on v.id=e.venue_id
where
    z.zipcode_from='92108' and
    z.distance <= 5
explain
select
    *
from
    zipcode_distances