mongodb - 通过销售记录，按商品分组，如何计算销售量和最近一次销售的价格?

问题描述

问 题

db.sales.insert({"商品":"上衣","销售时间":"2015-12-01 11:00","售价":1.3});
db.sales.insert({"商品":"上衣","销售时间":"2015-12-01 12:00","售价":1.4});
db.sales.insert({"商品":"裤子","销售时间":"2015-12-01 11:30","售价":2.3});
db.sales.insert({"商品":"裤子","销售时间":"2015-12-01 12:30","售价":2.4});
db.sales.insert({"商品":"鞋子","销售时间":"2015-12-01 11:00","售价":3.3});
db.sales.insert({"商品":"鞋子","销售时间":"2015-12-01 12:00","售价":3.4});
db.sales.insert({"商品":"鞋子","销售时间":"2015-12-01 12:30","售价":3.5});

db.sales.aggregate([
   { $group: { 
       _id: "$商品", 
       "销售量":{$sum:1} ,
       "最后销售时间": { $max: "$销售时间" } 
   } }
]);

问题：如何求最后销售时间对应的售价？

解决方案

Hope this helps.

Love MongoDB! Have Fun!

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