ModelsDatabasesRelationships.md

## Models, Databases, Relationships in Rails

#### What is the difference between a primary key and a foreign key? Where would we find a primary key? What would it be called by default? Where would we find a foreign key? What is the naming convention for a foreign key?
  We find a primary key as the main identifier of a table. Example: Teachers: TeacherId. A Foreign creates the relationship between tables.
  Example: Teachers : course_id. The naming convention for these are the table they  belong to + "_id" 

#### Write down one example of:
* a `one-to-one `relationship.
  each person has one toothbrush and one toothbrush has one person. This is modeled by combining both to a single table because they are 
  dependent of eachother
* a `one-to-many relationship`.
  Person can have many pants, but pants have one person.. Always in a one-to-many relationship, the many gets the foreign_key of the one
* a `many-to-many relationship`.
A Book can have many authors and an author can have many books. This is modeled by creating a join table of each tables primary key


### How do you create a rails app from the command line with postgres database? 
rails new appname --database=postgresql

### Whats the difference between test, devleopment and production databases? 
depending where you are sending the data from (test, dev, production) it will be stored in a seperare database. By keeping these seperate,
you can have specific databases and limit confusion. You wouldn't want test data in your production database. 

## What files are created by typing rails g model
it created the model, migration, fixtures and model test file.