It is now even simpler: PostgreSQL 9.4 introduced the mode()
function:
select mode() within group (order by food_id)
from munch
group by country
returns (like user2247323’s example):
country | mode
--------------
GB | 3
US | 1
See documentation here:
https://wiki.postgresql.org/wiki/Aggregate_Mode
https://www.postgresql.org/docs/current/static/functions-aggregate.html#FUNCTIONS-ORDEREDSET-TABLE