Ruby on Rails Q & A


What is the difference between `find` and `where` in Rails?

In Rails’ ActiveRecord, both `find` and `where` are methods used to retrieve data from the database. However, they serve different purposes and have distinct behaviors:


  1. Usage:


   – find: This method is primarily used to retrieve records by their primary key. For instance, `User.find(1)` will return the user with an ID of 1.

   – where: This method allows for more general queries and returns an ActiveRecord relation. For example, `User.where(first_name: ‘John’)` retrieves all users with the first name ‘John’.


  1. Return Value:


   – find: It returns a single record when given a single ID or multiple records when provided with an array of IDs. For instance, `User.find(1, 2)` returns the users with IDs 1 and 2.

   – where: Always returns an ActiveRecord::Relation, even if only one record matches the query. This means you can chain additional query methods onto it.


  1. Handling No Matches:


   – find: If no record is found, it raises an `ActiveRecord::RecordNotFound` exception. This often translates to a 404 error in a Rails application.

   – where: If no records match the criteria, it returns an empty ActiveRecord::Relation, not an error.


  1. Flexibility:


   – find: Primarily suited for lookups by primary key.

   – where: Offers flexibility in forming conditions. For instance, you can use SQL-like fragments such as `User.where(“created_at > ?”, – 7.days)`.


  1. Chaining:


   – find: Cannot be chained with other query methods because it doesn’t return an ActiveRecord relation (unless you’re using `find_by` which is a different method but similar in behavior to `where`).

   – where: Easily chainable with other ActiveRecord query methods like `order`, `limit`, and `group`.


While both `find` and `where` help retrieve data in Rails, they have different use cases. `find` is specific and direct, ideal for retrieving by ID, whereas `where` provides a flexible and chainable approach suitable for more complex queries.

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Senior Software Engineer with a focus on remote work. Proficient in Ruby on Rails. Expertise spans y6ears in Ruby on Rails development, contributing to B2C financial solutions and data engineering.