Question

在原始的MySQL查询中，我有类似的东西：

Select total_sales - over_head_costs As net_sales from departments;

如何通过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

Bookshelf没有此功能，但它带来了一个插件：Virtuals 。无需安装任何内容，只需在使用bookshelf.plugin('virtuals')加载Bookshelf后立即加载。

您的模型应该如下所示：

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());
  },
});

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