aggregation framework - using MongoDB aggregate count subdata -


here data in mongodb:

{     "data": {     "order_goods": [{         "category": 235     }, {         "category": 666     }]     } }, {     "data": {     order_goods: [{         "category": 235     }]     } }

here expected output:

{"category":235, "total":2} {"category":666, "total":1}

i have try many ways aggregate such $group, result like:

{ "_id" : [ 235, 666 ], "total" : 1 } { "_id" : [ 235 ], "total" : 1 }

thanks help.

please try below query :

db.collection.aggregate(  [   { "$unwind": "$data.order_goods" },   { "$group" : { "_id" : "$data.order_goods.category",      "total": {"$sum":1} } },   { "$project" : { "category" : "$_id" , total : 1 }  ]  );

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