BookShelf orm MySQL如何选择column1-column2作为别名

Question

在一个原始的 MySQL 查询中，我有这样的东西：

Select total_sales - over_head_costs As net_sales from departments;

如何使用 BookShelf /knex 查询实现相同的功能？理想情况下不使用 knex.raw。

我的尝试涉及以下内容：

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

Bookshelf 没有此功能，但它提供了一个插件：Virtuals 。无需安装任何东西，您只需在使用 bookshelf.plugin('virtuals') 加载 Bookshelf 后立即加载它。

您的模型应如下所示：

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());
  },
});