Model Querying - Finders

Finder methods are the ones that generate SELECT queries.

By default, the results of all finder methods are instances of the model class (as opposed to being just plain JavaScript objects). This means that after the database returns the results, Sequelize automatically wraps everything in proper instance objects. In a few cases, when there are too many results, this wrapping can be inefficient. To disable this wrapping and receive a plain response instead, pass { raw: true } as an option to the finder method.

findAll

The findAll method is already known from the previous tutorial. It generates a standard SELECT query which will retrieve all entries from the table (unless restricted by something like a where clause, for example).

findByPk

The findByPk method obtains only a single entry from the table, using the provided primary key.

const project = await Project.findByPk(123);
if (project === null) {
  console.log('Not found!');
} else {
  console.log(project instanceof Project); // true
  // Its primary key is 123
}

findOne

The findOne method obtains the first entry it finds (that fulfills the optional query options, if provided).

const project = await Project.findOne({ where: { title: 'My Title' } });
if (project === null) {
  console.log('Not found!');
} else {
  console.log(project instanceof Project); // true
  console.log(project.title); // 'My Title'
}

findOrCreate

The method findOrCreate will create an entry in the table unless it can find one fulfilling the query options. In both cases, it will return an instance (either the found instance or the created instance) and a boolean indicating whether that instance was created or already existed.

The where option is considered for finding the entry, and the defaults option is used to define what must be created in case nothing was found. If the defaults do not contain values for every column, Sequelize will take the values given to where (if present).

Let's assume we have an empty database with a User model which has a username and a job.

const [user, created] = await User.findOrCreate({
  where: { username: 'sdepold' },
  defaults: {
    job: 'Technical Lead JavaScript'
  }
});
console.log(user.username); // 'sdepold'
console.log(user.job); // This may or may not be 'Technical Lead JavaScript'
console.log(created); // The boolean indicating whether this instance was just created
if (created) {
  console.log(user.job); // This will certainly be 'Technical Lead JavaScript'
}

findAndCountAll

The findAndCountAll method is a convenience method that combines findAll and count. This is useful when dealing with queries related to pagination where you want to retrieve data with a limit and offset but also need to know the total number of records that match the query.

The findAndCountAll method returns an object with two properties:

• count - an integer - the total number records matching the query
• rows - an array of objects - the obtained records

const { count, rows } = await Project.findAndCountAll({
  where: {
    title: {
      [Op.like]: 'foo%'
    }
  },
  offset: 10,
  limit: 2
});
console.log(count);
console.log(rows);