如何使用Active Record查詢來計算總字符串值/組？

Question

有沒有一種方法可以使用Active Record（使用PostgreSQL作為數據庫）來計算數據庫列中有多少個特定的字符串值？

如果要在我的view中顯示世界上有多少塔科愛好者。

例如：

# Where the number "2" was an ActiveRecord count in the Persons table
# reading from the column named "favorite_food"

<div class="notice">
  <p>There are 2 burrito lovers online</p>
</div>

通過查看ActiveRecord文檔，我了解到了這一點：

# == Schema Information
#
# Table name: Persons
#
#  id                     :integer          not null, primary key
#  name                   :string           default(""), not null
#  age                    :integer          default(""), not null
#  favorite_food          :string

# Data
# Person id: 1, name: "John", age: "18", favorite_food: "taco"
# Person id: 2, name: "Jane", age: "19", favorite_food: "taco"
# Person id: 3, name: "Bill", age: "20", favorite_food: "burrito"
# Person id: 4, name: "Beth", age: "21", favorite_food: "nacho"

# This will record total unique foods
Person.count(:favorite_food)
=> 3

# This will return a hash with total name of distinct foods
Person.group(:favorite_food).count
=> {taco=>"2", "burrito"=>1, "nacho"=>1}

我認為最后一點已經接近了，但我想查詢一種特定的食物類型，如果可能的話，我將如何使用ActiveRecord進行查詢？ 我當時以為可以使用枚舉進行迭代，但這不是解決這種情況的最佳方法。

感謝您抽出寶貴時間來看看我的問題。

Answer 1

嘗試這個

Person.where(favorite_food: 'burrito').count