以排序形式从多个文档返回内部数组元素

乔琳

试试这个：

db.comments.aggregate([  {$match: {blog_id: ObjectId("56587befdb7224110f007233")}}, //match blogid  {"$unwind": "$comments"}, //unwind the comments array  {$sort: {"comments.dt": 1}}, //sort the comment documents by date  {    "$group": {        "_id": '$blog_id', //group comment documents by blog_id        "comments": { "$push": "$comments" //push comments of same blog_id into an array        }    }}])

根据您的样本数据，输出将是：

{    "_id" : ObjectId("56587befdb7224110f007233"),    "comments" : [        { "user_id" : ObjectId("562fa014888806820e21e0df"), "user_full_name" : "Niroj Paudel", "comment" : "wat a nice car wow", "_id" : ObjectId("565efa37635f09900d21a33a"), "dt" : ISODate("2015-12-02T14:03:35.289Z")        },        { "user_id" : ObjectId("562fa014888806820e21e0df"), "user_full_name" : "Niroj Paudel", "comment" : "love is life budikhola ma dives", "_id" : ObjectId("565efa76635f09900d21a33b"), "dt" : ISODate("2015-12-02T14:04:38.661Z")        },        { "user_id" : ObjectId("562fa014888806820e21e0df"), "user_full_name" : "Niroj Paudel", "comment" : "bholi ajaya ko bihe", "_id" : ObjectId("565efaa0635f09900d21a33c"), "dt" : ISODate("2015-12-02T14:05:20.847Z")        },        { "user_id" : ObjectId("562fa014888806820e21e0df"), "user_full_name" : "Niroj Paudel", "comment" : "manish is nice", "_id" : ObjectId("565efb17635f09900d21a33d"), "dt" : ISODate("2015-12-02T14:07:19.704Z")        },        { "user_id" : ObjectId("562fa014888806820e21e0df"), "user_full_name" : "Niroj Paudel", "comment" : "niroj is cool", "_id" : ObjectId("565efd53c22dddc80e8f461c"), "dt" : ISODate("2015-12-02T14:16:51.730Z")        },        { "user_id" : ObjectId("562fa014888806820e21e0df"), "user_full_name" : "Niroj Paudel", "comment" : "ramesh is cool", "_id" : ObjectId("565f0d376d82e24c11f6c0d1"), "dt" : ISODate("2015-12-02T15:24:39.010Z")        },        { "user_id" : ObjectId("562fa014888806820e21e0df"), "user_full_name" : "Niroj Paudel", "comment" : "pradip is bhole baba", "_id" : ObjectId("565f0f5d77f0c7bd11bbadd9"), "dt" : ISODate("2015-12-02T15:33:49.578Z")        },        { "user_id" : ObjectId("562fa014888806820e21e0df"), "user_full_name" : "Niroj Paudel", "comment" : "honkog pokhara... he he ha ha", "_id" : ObjectId("565f1034fd07cbfc1129db0b"), "dt" : ISODate("2015-12-02T15:37:24.581Z")        }    ]}