Sequelize select with two relations to the same entity - orm

Question

I have 2 tables, ItemLegacy :
module.exports = function(sequelize, DataTypes) {
return sequelize.define('ItemLegacy', {
id: {
type: DataTypes.INTEGER(11).UNSIGNED,
allowNull: false,
primaryKey: true
},
parent: {
type: DataTypes.INTEGER(11),
allowNull: false,
defaultValue: 0,
},
child: {
type: DataTypes.INTEGER(11),
allowNull: false,
defaultValue: 0
}
}, {
tableName: 'ItemLegacy',
timestamps: false,
underscored: false
});
};
and Item :
module.exports = function(sequelize, DataTypes) {
return sequelize.define('Item', {
id: {
type: DataTypes.INTEGER(11).UNSIGNED,
allowNull: false,
primaryKey: true
},
title: {
type: DataTypes.STRING(500),
allowNull: false,
defaultValue: ''
},
code: {
type: DataTypes.STRING(20),
allowNull: true
},
}, {
tableName: 'Item',
timestamps: false,
underscored: false
});
};
I also defined two relationships :
db.ccnLegacy.hasOne(db.ccn, { foreignKey: 'id', sourceKey: 'parent' })
db.ccnLegacy.hasOne(db.ccn, { foreignKey: 'id', sourceKey: 'child' })
My question is, I would like to create a select request using sequelize, with a relation for each of the 2 fields parent and child.
I know how to do that with one relation, but how do I do it with 2 ?
My code with only one relation :
db.itemLegacy.findOne({
raw: true,
where: { child: idChild },
include: [
{
model: db.item
},
]
})

Answer 1

You simply should indicate aliases for both associations and use them in queries. Second is you used hasOne instead of belongTo because belongTo is used exactly in a case when you go from N to 1 in N:1 relationship.
Associations:
db.ccnLegacy.belongsTo(db.ccn, { foreignKey: 'parent', as: 'Parent' })
db.ccnLegacy.belongsTo(db.ccn, { foreignKey: 'child', as: 'Child' })
Query:
db.itemLegacy.findOne({
raw: true,
where: { child: idChild },
include: [
{
model: db.item,
as: 'Child'
},
{
model: db.item,
as: 'Parent'
},
]
})