书架ORM的MySQL如何选择列1，列2的别名

Question

在原MySQL查询，我有这样的事情：

Select total_sales - over_head_costs As net_sales from departments; 

我怎样才能实现与书架/ knex查询同样的事情？理想情况下不使用knex.raw。

我尝试包括以下内容：

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

书架不具备此功能，但它带来的一个插件是：Virtuals 。无需安装任何东西，只需在使用bookshelf.plugin('virtuals')加载书架后立即加载它。

你的模型应该再像：

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()); 
    }, 
});