Writing Migrations with Foreign Keys Using SequelizeJS

How do I create tables with foreign key relationships with one another through the Sequelize QueryInterface?

The .createTable() method takes in a dictionary of columns. You can see the list of valid attributes in the documentation for .define(), specifically by looking at the [attributes.column.*] rows within the params table.

To create an attribute with a foreign key relationship, use the "references" and "referencesKey" fields:

For example, the following would create a users table, and a user_emails table which references the users table.

queryInterface.createTable('users', {
  id: {
    type: Sequelize.INTEGER,
    primaryKey: true,
    autoIncrement: true
  }
}).then(function() {
  queryInterface.createTable('user_emails', {
    userId: {
      type: Sequelize.INTEGER,
      references: { model: 'users', key: 'id' }
    }
  })
});

What columns and helper tables are required by sequelize? For example, it appears that specific columns such as createdAt or updatedAt are expected.

It appears that a standard model will expect an id, updatedAt, and createdAt column for each table.

queryInterface.createTable('users', {
  id: {
    type: Sequelize.INTEGER,
    primaryKey: true,
    autoIncrement: true
  },
  createdAt: {
    type: Sequelize.DATE
  },
  updatedAt: {
    type: Sequelize.DATE
  }
}

If you set paranoid to true on your model, you also need a deletedAt timestamp.

This is to create migration file for adding a column.

Here I want to add a column area_id in users table. Run command:

sequelize migration:create --name add-area_id-in-users

Once it gets executed creates a migration file timestamp-add-region_id-in-users in the migrations folder.

In the created migration file paste the below code:

'use strict';

module.exports = {
  up: (queryInterface, Sequelize) => {
        return Promise.all([
          queryInterface.addColumn('users', 'region_id',
            {
              type: Sequelize.UUID,
              references: {
                model: 'regions',
                key: 'id',
              },
              onUpdate: 'CASCADE',
              onDelete: 'SET NULL',
              defaultValue: null, after: 'can_maintain_system'
            }),
        ]);
      },

      down: (queryInterface, Sequelize) => {
        return Promise.all([
          queryInterface.removeColumn('users', 'region_id'),
        ]);
      }
    };

Here in the users table I am going to create a column named region_id along with type and relation/foreign key/references. That's it.

I want to offer another more manual alternative because when using manual migrations and queryInterface I ran across the following problem: I had 2 files in the migration folder like so

migrations/create-project.js
migrations/create-projectType.js

because project had column projectTypeId it referenced projectType, which wasnt created yet due to the order of the files and this was causing an error.

I solved it by adding a foreign key constraint after creating both tables. In my case I decided to write it inside create-projectType.js:

queryInterface.createTable('project_type', {
  // table attributes ...
})
.then(() => queryInterface.addConstraint('project', ['projectTypeId'], {
  type: 'FOREIGN KEY',
  name: 'FK_projectType_project', // useful if using queryInterface.removeConstraint
  references: {
    table: 'project_type',
    field: 'id',
  },
  onDelete: 'no action',
  onUpdate: 'no action',
}))