Get most common value for each value of another column in SQL

Question

I have a table like this:

 Column  | Type | Modifiers 
---------+------+-----------
 country | text | 
 food_id | int  | 
 eaten   | date | 

<

Answer 1

Here is a statement which I believe gives you what you want and is simple and concise:

select distinct on (country) country, food_id
from munch
group by country, food_id
order by country, count(*) desc

Please let me know what you think.

BTW, the distinct on feature is only available in Postgres.

Example, source data:

country | food_id | eaten
US        1         2017-1-1
US        1         2017-1-1
US        2         2017-1-1
US        3         2017-1-1
GB        3         2017-1-1
GB        3         2017-1-1
GB        2         2017-1-1

output:

country | food_id
US        1
GB        3