Migrations, Databases, Models, and Relationships in Rails

* Describe one-to-one, one-to-many, and many-to-many database relationships
  * one-to-one = a person has a SSN
  * one-to-many => the US has many states, the states belong to one country, 
  * many-to-many => a child has multiple parents, the parent has many children. a person can attend many events 
* Explain the difference between dev, test, and production environments in Rails
  * In development Rails runs on local machine so you can see data
  * Production mode is a public facing database
  * The test mode is used in the tests and is wiped clean between test runs
* How do you create a Rails app from the command line with a postgres database?
  * rails new appname --database=postgresql
* What files are created by typing rails g model Author first_name:text last_name:text?
	* db/migrate/20160217165920_create_authors.rb
	* app/models/author.rb
	* test/models/author_test.rb
  * test/fixtures/authors.yml
* What's the difference between typing rails g model ... and rails g migration ...?
  * model creates model and migration and two test files
  * migration only creates a migration. use this if only changing the migration
* Imagine that the items table has a category called quantity. 
  What command would you type if you wanted to get rid of the quantity attribute?
  * rails g migration RemoveQuantityFromItems quantity:integer
* Imagine that you have a table students. 
  What is the ActiveRecord query that would return all students with the first name of Richard?
  * Student.where(first_name: "Richard")
* How would you update the student record with ID 4 to have a new phone number of "101-222-3333"?
  * Student.find(4).update(phone_number: "101-222-3333")
  * Student.update(4, phone_number: "101-222-3333")
  * student = Student.find(4)
    student.phone_number = "101-222-3333"
    student.save