Before Rails 6, selecting only the first value for a column from a set of records was cumbersome. Let’s say we want only the first name from all the posts with category “Rails 6”.

>> Post.where(category: "Rails 6").limit(1).pluck(:name).first
   SELECT "posts"."name"
   FROM "posts"
   WHERE "posts"."category" = ?
   LIMIT ?  [["category", "Rails 6"], ["LIMIT", 1]]
=> "Rails 6 introduces awesome shiny features!"

In Rails 6, the new ActiveRecord::Relation#pick method has been added which provides a shortcut to select the first value.

>> Post.where(category: "Rails 6").pick(:name)
   SELECT "posts"."name"
   FROM "posts"
   WHERE "posts"."category" = ?
   LIMIT ?  [["category", "Rails 6"], ["LIMIT", 1]]
=> "Rails 6 introduces awesome shiny features!"

This method internally applies limit(1) on the relation before picking up the first value. So it is useful when the relation is already reduced to a single row.

It can also select values for multiple columns.

>> Post.where(category: "Rails 6").pick(:name, :author)
   SELECT "posts"."name", "posts"."author"
   FROM "posts"
   WHERE "posts"."category" = ?
   LIMIT ?  [["category", "Rails 6"], ["LIMIT", 1]]
=> ["Rails 6.0 new features", "prathamesh"]