Fetching Minimum/Maximum for each group in ActiveRecord

Question

This is an age-old question where given a table with attributes \'type\', \'variety\' and \'price\', that you fetch the record with the minimum price for each type there is.

Answer 1

You can use #find_by_sql, but this implies returning a model object, which might not be what you want.

If you want to go bare to the metal, you can also use #select_values:

data = ActiveRecord::Base.connection.select_values("
        SELECT f.type, f.variety, f.price
        FROM (SELECT type, MIN(price) AS minprice FROM table GROUP BY type ) AS x
        INNER JOIN table AS f ON f.type = x.type AND f.price = x.minprice")
puts data.inspect
[["type", "variety", 0.00]]

ActiveRecord is just a tool. You use it when it's convenient. When SQL does a better job, you use that.