GROUP BY and COUNT using ActiveRecord

by

Distinct and Group By are going to give you different results. To get the results you expect you’ll want to use

Person.group(:name).count
(1.2ms)  SELECT COUNT(*) AS count_all, name AS name FROM "people" GROUP BY "people"."name"
=> {"Dan"=>3, "Dave"=>2, "Vic"=>1}

Seen above, group will return things as a hash. While distinct just returns the number of people in total, seen below. 

Person.distinct(:name).count
(0.4ms)  SELECT DISTINCT COUNT(DISTINCT "people"."id") FROM "people"
=> 6

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