Sequelize: Model is not associated to Model2-CodePudding

I'm trying to make a query with a few models in Sequelize. I have 2 models, one is Project and the other one is Specification. A project can have many Specifications, and a specification can only belong to one project. The table structure is:

Project:

Title
Description
CreatedAt
UpdatedAt

Specification:

Title
Description
ProjectId (Foreign Key from Projects table)

This is the relation I have for Specifications -> Projects:

Project.belongsToMany(Specification);

The function i'm using to retrieve the data is this. Basically it gets all the data, including all the possible associations:

// Retrieve all Projects from the database.
exports.findAll = (req, res) => {
  Project.findAll({
  include: [{
    all: true
  }]
})
.then(data => {
  res.send(data);
})
.catch(err => {
  res.status(500).send({
    message:
      err.message || "Some error occurred while retrieving projects."
  });
});
};

Finally, the error I'm getting is this:

{"message":"specification is not associated to project!"}

Can someone help me or teach me about how to accomplish the query? I've been trying and cannot get the right result. Thank you!

CodePudding user response：

If you describe your structure as

A project can have many Specifications, and a specification can only belong to one project

then it's a usual 1:N relationship and in this case, hasMany association should be used instead of belongsToMany because belongsToMany is used to indicate M:N relationship and in that case, you will need a junction table/model. That said you only need to replace

Project.belongsToMany(Specification);

with

Project.hasMany(Specification, { foreignKey: 'ProjectId' });

I always prefer to indicate a foreign key explicitly