GROUP BY and COUNT using ActiveRecord

Question

Refering to this: Is there any difference between GROUP BY and DISTINCT

Given a table that looks like this:  name ------ barry dave bill dave dave barry john This query:  SELECT name, count(*) AS count FROM table GROUP BY name; Will produce output like this:  name    count ------------- barry   2 dave    3 bill    1 john    1 

What is the correct Rails convention here for ActiveModel to perform a GROUP BY with COUNT?

Answer 1

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