CODEWITHSUNDEEP
mongodbmongodb-queryaggregation-framework
YAM
YAM

Reputation: 494

find the documents with distinct and sorting in mongoDB?

I have this sample json:

{
     "_id" : ObjectId("56de78e0c8f8759239f20cc8"),    
     "vendor_Name" : "bb group trades",     
     "parrent_id" : "56d6c4400a5eac8a78101c8f",
     "channel_name" : "snapdeal",
     "create_date" : ISODate("2016-03-07T18:30:00.000Z"),
     "product_rating" : "3.9" 
}, 

{
    "_id" : ObjectId("56de7b29c8f8759239f20cca"),
    "vendor_Name" : "bb group trades",
    "parrent_id" : "56d6e2594e8ee6111417e67a",
    "channel_name" : "snapdeal",
    "create_date" : ISODate("2016-03-07T18:30:00.000Z"),
    "product_rating" : null 
},

{
    "_id" : ObjectId("56de7b1ac8f8759239f20cc9"),
    "vendor_Name" : "oyedeal",   
    "parrent_id" : "56d6e2594e8ee6111417e67a",
    "channel_name" : "snapdeal",
    "create_date" : ISODate("2016-03-07T18:30:00.000Z"),
    "product_rating" : "5.0" 
}

I want to fetch the documents which have distinct parrent_id and have oldest create_date

How I can Do this?

Upvotes: 0

Views: 250

Answers (1)

zangw
zangw

Reputation: 48356

Please try this one. Firstly, sort the create_date in ascending order, and group by parrent_id and pick the oldest record for each parrent_id to meet distinct requirement.

db.collection.aggregate([
                         // sort the create_date in ascending order
                         {$sort: {create_date: 1}},
                         // group by `parrent_id`, and pick the first element for each field which is the oldest create_date.
                         {$group: {_id: '$parrent_id',
                                   'vendor_Name': {$first: '$vendor_Name'},
                                   'channel_name': {$first: '$channel_name'},
                                   'product_rating': {$first: '$product_rating'}
                                   }
                        }]);

Upvotes: 1

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