Creating with Associations

An instance can be created with nested association in one step, provided all elements are new.

In contrast, performing updates and deletions involving nested objects is currently not possible. For that, you will have to perform each separate action explicitly.

BelongsTo / HasMany / HasOne association

Consider the following models:

class Product extends Model {}
Product.init({
  title: DataTypes.STRING
}, { sequelize, modelName: 'product' });
class User extends Model {}
User.init({
  firstName: DataTypes.STRING,
  lastName: DataTypes.STRING
}, { sequelize, modelName: 'user' });
class Address extends Model {}
Address.init({
  type: DataTypes.STRING,
  line1: DataTypes.STRING,
  line2: DataTypes.STRING,
  city: DataTypes.STRING,
  state: DataTypes.STRING,
  zip: DataTypes.STRING,
}, { sequelize, modelName: 'address' });

// We save the return values of the association setup calls to use them later
Product.User = Product.belongsTo(User);
User.Addresses = User.hasMany(Address);
// Also works for `hasOne`

A new Product, User, and one or more Address can be created in one step in the following way:

return Product.create({
  title: 'Chair',
  user: {
    firstName: 'Mick',
    lastName: 'Broadstone',
    addresses: [{
      type: 'home',
      line1: '100 Main St.',
      city: 'Austin',
      state: 'TX',
      zip: '78704'
    }]
  }
}, {
  include: [{
    association: Product.User,
    include: [ User.Addresses ]
  }]
});

Observe the usage of the include option in the Product.create call. That is necessary for Sequelize to understand what you are trying to create along with the association.

Note: here, our user model is called user, with a lowercase u - This means that the property in the object should also be user. If the name given to sequelize.define was User, the key in the object should also be User. Likewise for addresses, except it's pluralized being a hasMany association.

BelongsTo association with an alias

The previous example can be extended to support an association alias.

const Creator = Product.belongsTo(User, { as: 'creator' });

return Product.create({
  title: 'Chair',
  creator: {
    firstName: 'Matt',
    lastName: 'Hansen'
  }
}, {
  include: [ Creator ]
});

HasMany / BelongsToMany association

Let's introduce the ability to associate a product with many tags. Setting up the models could look like:

class Tag extends Model {}
Tag.init({
  name: DataTypes.STRING
}, { sequelize, modelName: 'tag' });

Product.hasMany(Tag);
// Also works for `belongsToMany`.

Now we can create a product with multiple tags in the following way:

Product.create({
  id: 1,
  title: 'Chair',
  tags: [
    { name: 'Alpha'},
    { name: 'Beta'}
  ]
}, {
  include: [ Tag ]
})

And, we can modify this example to support an alias as well:

const Categories = Product.hasMany(Tag, { as: 'categories' });

Product.create({
  id: 1,
  title: 'Chair',
  categories: [
    { id: 1, name: 'Alpha' },
    { id: 2, name: 'Beta' }
  ]
}, {
  include: [{
    association: Categories,
    as: 'categories'
  }]
})