mongodb - 聚合/分组 w/a Sum

Question

我正在努力了解 Mongo 的整个聚合框架。我在这里有点新手。

 I have the following documents:
 { "col1": "camera", "fps": 1, "lat": 3 },
 { "col1": "camera", "fps": 3, "lat": 2 }
 { "col1": "recorders", "fps": 9, "lat": 7 }
 { "col1": "cell", "fps": 8, "lat": 1 }
 { "col1": "cell", "fps": 4, "lat": 3 }

如何设置返回结果:

 { "col1": "camera", "fps": 4, "lat": 5 },
 { "col1": "recorders", "fps": 9, "lat": 7 },
 { "col1": "cell", "fps": 12, "lat": 4 },

谢谢

Answer 1

db.yourCollection.aggregate(
    { $group : {
        _id : "$col1",
        fps : { $sum : "$fps" },
        lat : { $sum : "$lat" }
    }}
);

看看这个!!! http://docs.mongodb.org/manual/reference/operator/aggregation/group/