How to fetch associated data with models generated form Sequalize? - mysql

Question

I have been developing a NodeJs backend application with an MySQL support with Sequelize as the ORM. I'm trying to fetch data by calling an API that I have created. It sends the data as an response. But it doesn't containg the associated object related to the foriegn key relationships.
I already had a MySQL database and I was using sequelize ORM, I used sequelize-auto to generate the model classes. All the model classes were generated successfully. But the associations were not generated with the models. Therefore to cater to the associations I had to manually add the associations to the model class. Then I create the route files and created the HTTP GET method. But the API endpoint doesn't send the data as expected.
following shows the model classes and route files that I have created.
module.exports = function(sequelize, DataTypes) {
const Department = sequelize.define('Department', {
department_id: {
type: DataTypes.INTEGER(11),
allowNull: false,
primaryKey: true,
autoIncrement: true
},
name: {
type: DataTypes.STRING(100),
allowNull: false
},
description: {
type: DataTypes.STRING(1000),
allowNull: true
}
}, {
tableName: 'department',
timestamps: false,
underscored: true
});
Department.associate = function(models) {
// associations can be defined here
Department.hasMany(models.Category, {
foreignKey: 'department_id',
as: 'categories',
});
};
return Department;
};
module.exports = function(sequelize, DataTypes) {
const Category = sequelize.define('Category', {
category_id: {
type: DataTypes.INTEGER(11),
allowNull: false,
primaryKey: true,
autoIncrement: true
},
department_id: {
type: DataTypes.INTEGER(11),
allowNull: false
},
name: {
type: DataTypes.STRING(100),
allowNull: false
},
description: {
type: DataTypes.STRING(1000),
allowNull: true
}
}, {
tableName: 'category',
timestamps: false,
underscored: true
});
Category.associate = function(models) {
// associations can be defined here
Category.belongsTo(models.Department)
};
return Category;
};
var express = require('express');
var router = express.Router();
var model = require('../models/index');
/* GET departments listing. */
router.get('/', function(req, res, next) {
model.Department.findAll({})
.then(department => res.json({
error: false,
data: department
}))
.catch(error => res.json({
data: [],
error: true
}));
});
module.exports = router;
var express = require('express');
var router = express.Router();
var model = require('../models/index');
/* GET category listing. */
router.get('/', function(req, res, next) {
model.Category.findAll({})
.then(category => res.json({
error: false,
data: category
}))
.catch(error => res.json({
data: [],
error: true
}));
});
module.exports = router;
Response for /department route
{
"error": false,
"data": [
{
"department_id": 1,
"name": "Regional",
"description": "Proud of your country? Wear a T-shirt with a national symbol stamp!"
},
{
"department_id": 2,
"name": "Nature",
"description": "Find beautiful T-shirts with animals and flowers in our Nature department!"
},
{
"department_id": 3,
"name": "Seasonal",
"description": "Each time of the year has a special flavor. Our seasonal T-shirts express traditional symbols using unique postal stamp pictures."
}
]
}
Response for /category route
{
"data": [],
"error": true
}
I was expecting data to come with associated objects as well. But it doesn't send the data as expected. What have I done wrong here.

Answer 1

The thing here is that you are not saying on the query that you need the associate data. To do this you have to use include inside the findAll() function.
/* GET departments listing. */
router.get('/', function(req, res, next) {
model.Department.findAll({
include: [{
model: model.Category
as: 'categories'
}]
})
.then(department => res.json({
error: false,
data: department
}))
.catch(error => res.json({
data: [],
error: true
}));
});
Edit:
I saw that you changed the default primary key for the models, so you also has to specify that on the Category association. Sequelize by default only works with one way association, on your case from Deparment to Category. Sequelize doesn't know about Deparment foreignkey on Category, even when you defined it. You have to define which key are you pointing.
Category.associate = function(models) {
// associations can be defined here
Category.belongsTo(models.Department, {as: 'department', foreignKey: 'department_id'})
};