Rails: select unique values from a column

Question

I already have a working solution, but I would really like to know why this doesn\'t work:

ratings = Model.select(:rating).uniq
ratings.each { |r| puts r.rat         


        

Answer 1

Model.pluck("DISTINCT column_name")

Answer 2

Model.uniq.pluck(:rating)

# SELECT DISTINCT "models"."rating" FROM "models"

This has the advantages of not using sql strings and not instantiating models

Answer 3

Model.select(:rating).distinct

Answer 4

This works too.

Model.pluck("DISTINCT rating")

Answer 5

If you want to also select extra fields:

Model.select('DISTINCT ON (models.ratings) models.ratings, models.id').map { |m| [m.id, m.ratings] }

Answer 6

Some answers don't take into account the OP wants a array of values

Other answers don't work well if your Model has thousands of records

That said, I think a good answer is:

    Model.uniq.select(:ratings).map(&:ratings)
    => "SELECT DISTINCT ratings FROM `models` " 

Because, first you generate a array of Model (with diminished size because of the select), then you extract the only attribute those selected models have (ratings)