Data Associations

• will allow us to have multiple pieces of data, multiple collections in our database that are related to one another --- important to making more complicated apps
  • example: with a site like Facebook there are models for User, Post, Photos, Albums , Comments, Tags, Likes, etc.
    • all these are interconnected

Types of Associations

• one:one relationships
  • simplest
  • have one of an entity that is related to one of another entity
    • examples:
      • one book has one publisher
      • one employee has one title
• one:many relationships
  • one entity is related to many of another entity
    • example:
      • Facebook --- one user can have multiple photos, but the photos only belong to one user
• many:many relationships
  • examples:
    • school --- each student has multiple courses, but each course also has multiple students
    • an author can have many books, but books can also have multiple authors

Embedding Data

• note: examples use Mongoose --- they will use User and Posts to model a one:many relationship
• examples located in 'the-web-developer-bootcamp/15_data_associations/embed.js'
• this gives us users that look like this:

{
  email:'asdas',
  name: 'asdas',
  posts: [
    {title: 'asdas', content: 'asdas'},
    {title: 'asdas', content: 'asdas'},
    {title: 'asdas', content: 'asdas'}
  ]
}

Referencing Data

• note: examples use Mongoose --- they will use User and Posts to model a one:many relationship
• examples located in 'the-web-developer-bootcamp/15_data_associations/references.js'
• now we will have users that look like this:

{
  email:'asdas',
  name: 'asdas',
  posts: [
    23578125876578,     // a list of ids that correrspond to individual posts rather than having
    256873456tg745,     // the whole post in the array (i.e. referencing the post)
    32fu4745974584,
    45628yuuihrwte
  ]
}
{
  id: 23578125876578,
  title: 'asdas',
  content: 'asdas'
}

Embed or Reference?

• can use either in almost all situations, but one usually lends itself better to what needs to be done in the particular situation

Module.Exports

• will help clean up code and make it more modular