BookShelf orm MySQL如何選擇column1-column2作為別名

Question

在原始MySQL查詢中，我有類似以下內容：

Select total_sales - over_head_costs As net_sales from departments;

如何通過BookShelf / knex查詢實現同一件事？ 理想情況下，不使用knex.raw。

我的嘗試包括：

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

書架沒有此功能，但它為此提供了一個插件： Virtuals 。 無需安裝任何東西，只需在使用bookshelf.plugin('virtuals')加載Bookshelf之后立即加載它。

您的模型應如下所示：

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());
  },
});