Exit Ticket: Day 9 - ORMs (Sequelize), Wikistack Pt 1

You should be able to:

• Define an ORM, and explain its pros/cons
• Define models in Sequelize
• Associate models with each other
• Hook into Sequelize lifecycle events
• Query on models (findAll, findOne, create, "magic methods", etc)

Sequelize is...

	Option	Explanation
☑️	A type of ORM
	A type of database	It just helps us connect to a database. It's not the database itself.
☑️	A library that converts between tables/rows and classes/instances
☑️	Used in Node applications to connect to SQL databases
	Used in Node applications to connect to ANY type of database	For NoSQL DBs such as Document Store (MongoDB), we would need to use a ODM (Object Data Modeling). In the case of MongoDB, the equivalent would be Mongoose.

Fill in the blanks in the code sample:

The model should be defined, the name attribute should not be allowed to be null, its type should be a text type and pictureURL should be a string type.

const User = db._____('user', {
    name: {
        type: Sequelize._____,
        _____: false
    },
    pictureUrl: _____.TEXT
})

• define, STRING, allowNull, Sequelize ☑️

  const User = db.define('user', {
      name: {
          type: Sequelize.STRING,
          allowNull: false
      },
      pictureUrl: Sequelize.TEXT
  })

• Sequelize, TEXT, isNotEmpty, define
• define, TEXT, isNotNull, Sequelize
• define, STRING, allowNull, global

Model Associations

A journal app has three entities, Author, Entry and Tag. There is a one-to-one relationship between Author and Pseudonym, a one-to-many relationship between Author and Entry and a many-to-many relationship between Tag and Entry. Choose the correct method for these relationships below.

	hasOne	hasMany	belongsToMany
Author to Entry		☑️
Author to Pseudonym	☑️
Entry to Tag			☑️

Pick the option which lists Sequelize model instance hooks in order:

• beforeValidate, afterDestroy, beforeCreate
• afterCreate, beforeDestroy, beforeValidate
• beforeValidate, afterValidate, beforeCreate ☑️
• beforeDestroy, beforeCreate, beforeValidate, afterUpdate

Extra resources:

• Julissa's Hooks and Ops Gist
• Sequelize: Hooks (official documentation)

Choose the method that will return exactly one instance in a query and not modify the database:

• findAll
• findOne ☑️
• create