Sequelize syntax reference

sequelize.js

// How to import from sequelize
const { Sequelize, DataTypes } = require('sequelize');

// How to instantiate a connection pool to sqlite
const sequelize = new Sequelize('sqlite::memory:', { logging: false });

// How to define a table
const Account = sequelize.define('Account', {
  type: { type: DataTypes.ENUM('savings', 'checking'), allowNull: false },
  name: { type: DataTypes.STRING, allowNull: false },
  balance: { type: DataTypes.INTEGER, allowNull: false, defaultValue: 0 },
});

// How to define a reciprocal relationship between two tables
Account.hasMany(Transaction, { foreignKey: 'accountId', as: 'transactions' });
Transaction.belongsTo(Account, { foreignKey: 'accountId', as: 'account' });

// How to run a fairly complex query. When not found, account is null.
const account = await Account.findByPk(req.params.account_id, {
  include: [{ model: Transaction, as: 'transactions' }], // LEFT JOIN
  order: [[{ model: Transaction, as: 'transactions' }, 'createdAt', 'DESC']],
});

// How to decrement an integer
await instance.decrement('balance', { by: amount });

// How to decrement an integer within a transaction
await instance.decrement('balance', { by: amount, transaction: t });

// How to start look-before-you-leap in a transaction
const instance = await Account.findByPk(fromAccountId, { transaction: t, lock: t.LOCK.UPDATE });