Table of Contents
How do I use references in Ruby on Rails?
Ruby on Rails
- Add a new column to a table.
- Add a new column with an index.
- Add a reference column to a table.
- Add a self reference.
- Add an unique column to a table.
- Add column with default value.
- Adding a NOT NULL constraint to existing data.
- Adding multiple columns to a table.
How do I add a foreign key in migration Rails?
How To Add A Foreign Key in Ruby on Rails
- rails new foreign_key rails g scaffold expense title:string amount:decimal rake db:migrate.
- rails g migration add_category_id_to_expenses category_id:integer rake db:migrate.
- class Expense < ActiveRecord::Base belongs_to :category end.
How do I add a reference column in Rails?
When you already have users and uploads tables and wish to add a new relationship between them. Then, run the migration using rake db:migrate . This migration will take care of adding a new column named user_id to uploads table (referencing id column in users table), PLUS it will also add an index on the new column.
Which database is best for Rails?
Which SQL database to choose for Ruby on Rails project?
- PostgreSQL: it’s one of the most cost-efficient, performing, and versatile SQL databases out there.
- SQLite is supported by Ruby on Rails by default as a highly compatible database.
- MySQL: arguably the most popular SQL database right now.
What is active record?
In Active Record, objects carry both persistent data and behavior which operates on that data. Active Record takes the opinion that ensuring data access logic as part of the object will educate users of that object on how to write to and read from the database.
What are the naming conventions used in active record?
By default, Active Record uses some naming conventions to find out how the mapping between models and database tables should be created. Rails will pluralize your class names to find the respective database table.
How do I change the attributes of an active record?
Once an Active Record object has been retrieved, its attributes can be modified and it can be saved to the database. A shorthand for this is to use a hash mapping attribute names to the desired value, like so: This is most useful when updating several attributes at once.
How to delete an active record from the database?
Likewise, once retrieved an Active Record object can be destroyed which removes it from the database. If you’d like to delete several records in bulk, you may use destroy_by or destroy_all method: Active Record allows you to validate the state of a model before it gets written into the database.