sequelizecheatsheet.md

Sequelize Cheat Sheet

Sequelize documentation is horrendous, so here's a handy cheat sheet.

Sequelize/PostgreSQL commands

Create a database

createdb database_name

Initialize Sequelize

sequelize init

Create a Sequelize Model

NOTE: The model name will be singular

NOTE 2: Any foreign keys will be modelNameId

• example: a foreign key to an author model will be authorId

sequelize model:create --name comment --attributes author:string,content:text,favoriteId:integer

Create a Sequelize Migration (empty by default)

sequelize migration:create --name migrationName

Run all Sequelize migrations

sequelize db:migrate

Undo latest Sequelize migration

sequelize db:migrate:undo

Sequelize Querying (using a comment model)

Create

db.favorite.create({
  author: 'Brian',
  content: 'A comment'
}).then(function(favorite) {
  //code here
});

Find or Create

//returns the instance if exists, otherwise creates it

db.favorite.findOrCreate({
  where: {
    author: 'Brian'
  },
  defaults: {
    content: 'A comment'
  }
}).spread(function(favorite, created) {
  //code here
});

Find

//returns only one instance; the first one that matches the where clause

db.favorite.find({
  where: {
    author: 'Brian'
  }
}).then(function(favorite) {
  //code here
});

Find + Eager Load

//returns only one instance, and loads all the comments associated with the favorite

db.favorite.find({
  where: {
    author: 'Brian'
  },
  include: [db.comment]
}).then(function(favorite) {
  // favorite.comments will exist, allowing access to the comments
});

Find All

//returns all instances that match the where clause

db.favorite.findAll({
  where: {
    author: 'Brian'
  }
}).then(function(favorite) {
  //code here
});

Find By Id

db.favorite.findById(1).then(function(favorite) {
  //code here
});

Find One

//returns only one instance

db.favorite.findOne().then(function(favorite) {
  //code here
});

Update

db.favorite.update({
  name: 'Josh'
  }, {
  where: {
    author: 'Brian'
  }
}).then(function(favorite){
  // do something after update
});

Destroy

db.favorite.destroy({
  where: {
    author: 'Brian'
  }
}).then(function() {
  // do something after destruction
});

Associations

1:M

Adding associations (using author and post models)

author.js

Authors should have many posts

associate: function(models) {
  models.author.hasMany(models.post);
}

post.js

A post should belong to an author

associate: function(models) {
  models.post.belongsTo(models.author);
}

M:M

Adding associations (using post and tag models, with a join table called postsTags)

post.js

A post should belong to many tags

associate: function(models) {
  models.post.belongsToMany(models.tag, {through: 'postsTags'});
}

tag.js

A tag should belong to many posts

associate: function(models) {
  models.tag.belongsToMany(models.post, {through: 'postsTags'})
}

Helper Functions (using a post model)

• createPost() - should create a post when called on a model related to post. Takes attributes as parameters
• getPosts() - should get posts when called on a model related to post
• addPost(post) - should add an existing post when called on a model related to post
• setPost([post1, post2]) - should delete all existing associations and add the array of posts when called on a model related to post

Promises

then

This is the default promise called when a query is completed.

spread

This is used to spread an array of values to parameters. This is only used for findOrCreate, where the callback has two parameters.

catch

This is triggered if something goes wrong (an error).

finally

This is triggered after all other callbacks (including then, spread, and catch). Can be used for cleanup.