BookShelf orm MySQL how to select column1-column2 as alias - mysql

Question

In a raw MySQL query, I have something like this:
Select total_sales - over_head_costs As net_sales from departments;
How can I realize the same thing with BookShelf /knex query? Ideally not using knex.raw.
My attempt involves following:
let Department = bookshelf.Model.extend({
tableName: 'departments',
idAttribute: 'department_id',
},{
getDepartments: function(){
return this.fetchAll({columns: ['department_id', 'department_name', 'over_head_costs', 'total_sales - over_head_costs AS net_sales']})
.then(models=>models.toJSON());
},
});

Answer 1

Bookshelf does not have this feature but it brings a plugin for that: Virtuals
. No need to install anything, you just load it right after loading Bookshelf using bookshelf.plugin('virtuals').
Your model should then look like:
const Department = bookshelf.Model.extend({
tableName: 'departments',
idAttribute: 'department_id',
virtuals: {
net_sales: function() {
return this.get('total_sales') - this.get('over_head_costs');
}
}
},{
getDepartments: function(){
return this.fetchAll({columns: ['department_id', 'department_name', 'over_head_costs', 'net_sales']})
.then(models=>models.toJSON());
},
});