What is ActiveRecord Query?
Active Record insulates you from the need to use SQL in most cases. Active Record will perform queries on the database for you and is compatible with most database systems, including MySQL, MariaDB, PostgreSQL, and SQLite.
What is an ActiveRecord relation?
Having queries return an ActiveRecord::Relation object allows us to chain queries together and this Relation class is at the heart of the new query syntax. This class contains the methods that we use in the new query syntax: includes , select , group , order , joins and so on.
What is ActiveRecord class?
Active Record Class This pattern allows information to be retrieved, inserted, and updated in your database with minimal scripting. In some cases only one or two lines of code are necessary to perform a database action.
Why we use include in Rails?
Rails provides an ActiveRecord method called :includes which loads associated records in advance and limits the number of SQL queries made to the database. This technique is known as “eager loading” and in many cases will improve performance by a significant amount.
What is Activemodel?
Active Model allows for Action Pack helpers to interact with plain Ruby objects. Active Model also helps build custom ORMs for use outside of the Rails framework.
What is the difference between Has_one and Belongs_to?
They essentially do the same thing, the only difference is what side of the relationship you are on. If a User has a Profile , then in the User class you’d have has_one :profile and in the Profile class you’d have belongs_to :user .
What does @variable mean in Ruby?
In Ruby, the at-sign ( @ ) before a variable name (e.g. @variable_name ) is used to create a class instance variable. These variables are: Specific to each instantiated object of the class they’re defined in (i.e. each class object instance has a separate copy of these variables).
Is include the same as JOIN?
In a sense, yes. Include is implemented as a join. Depending on the nullability of the included link it is an inner or left join.
What is difference between joins and include in Rails?
Includes uses eager loading whereas joins uses lazy loading. Both are used when certain operations are meant to be performed on associated tables.