Wil Chung iamwilhelm

'Include' in Sequelize: The One Confusing Query That You Should Memorize

When querying your database in Sequelize, you'll often want data associated with a particular model which isn't in the model's table directly. This data is usually typically associated through join tables (e.g. a 'hasMany' or 'belongsToMany' association), or a foreign key (e.g. a 'hasOne' or 'belongsTo' association).

When you query, you'll receive just the rows you've looked for. With eager loading, you'll also get any associated data. For some reason, I can never remember the proper way to do eager loading when writing my Sequelize queries. I've seen others struggle with the same thing.

Eager loading is confusing because the 'include' that is uses has unfamiliar fields is set in an array rather than just an object.

So let's go through the one query that's worth memorizing to handle your eager loading.

The Basic Query

Programming Achievements: How to Level Up as a Developer

This gist is part of a blog post. Check it out at:

http://jasonrudolph.com/blog/2011/08/09/programming-achievements-how-to-level-up-as-a-developer

	// This file is MIT Licensed.
	//
	// Copyright 2017 Christian Reitwiessner
	// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
	// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
	// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF O

	module Counter exposing (..)

	import Html exposing (..)
	import Html.Attributes exposing (style)
	import Html.Events exposing (onClick)


	-- MODEL

	type alias Model = Int

	-- See this document for more information on making Pong:
	-- http://elm-lang.org/blog/pong
	import Color exposing (..)
	import Collage exposing (..)
	import Element exposing (..)
	import Keyboard
	import Text
	import Time exposing (..)
	import Window exposing (Size)
	import Html.App as App

	import Html exposing (..)
	import Keyboard
	import Window exposing (Size)
	import AnimationFrame

	import Task
	import Html.App as App

	import Collage exposing (..)
	import Element exposing (..)

	Computing
	Paul E. Ceruzzi
	ISBN: 9780262517676

	Modeling Business Processes
	Wil van der Aalst and Christian Stahl
	ISBN: 9780262015387

	The Reasoned Schemer
	Daniel P. Friedman, William E. Byrd, and Oleg Kiselyov

	Latency Comparison Numbers (~2012)
	----------------------------------
	L1 cache reference 0.5 ns
	Branch mispredict 5 ns
	L2 cache reference 7 ns 14x L1 cache
	Mutex lock/unlock 25 ns
	Main memory reference 100 ns 20x L2 cache, 200x L1 cache
	Compress 1K bytes with Zippy 3,000 ns 3 us
	Send 1K bytes over 1 Gbps network 10,000 ns 10 us
	Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD

	/**
	* Modified from the Connect project: https://github.com/senchalabs/connect/blob/master/lib/middleware/errorHandler.js
	*
	* Flexible error handler, providing (_optional_) stack traces and logging
	* and error message responses for requests accepting text, html, or json.
	*
	* Options:
	*
	* - `showStack` respond with both the error message and stack trace. Defaults to `false`
	* - `showMessage`, respond with the exception message only. Defaults to `false`