How to Retrieve the Top 5 Most Listened-to Songs Using ActiveRecord Associations?

Ordering ActiveRecord Records by Association Count

In Rails 3, you can easily access and manipulate data from related tables using the ActiveRecord framework. Consider the scenario where you want to retrieve the top 5 most listened-to songs from a model named Song. You have a separate model called Listen that establishes a one-to-many relationship between songs and listens.

To achieve the desired result, you can utilize the has_many and belongs_to associations in your models. A named scope provides a convenient way to define complex queries and reuse them throughout your application. Here's how you can implement it:

class Song
  has_many :listens

  scope :top5,
    select("songs.id, OTHER_ATTRS_YOU_NEED, count(listens.id) AS listens_count").
    joins(:listens).
    group("songs.id").
    order("listens_count DESC").
    limit(5)
end

In this code:

• select specifies the columns to be retrieved and adds a calculated listens_count column.
• joins establishes the relationship between Song and Listen.
• group groups the results by song ID to count the number of listens for each song.
• order arranges the results in descending order of listens_count.
• limit restricts the selection to the top 5 most listened songs.

Now, you can use the top5 method to easily retrieve the desired data:

Song.top5 # top 5 most listened songs

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