MongoDB nested group?

Question

I\'m trying to implement a nested group query in mongodb and I\'m getting stuck trying to add the outer group by. Given the below (simplified) data document:

Answer 1

You will need two groups in this case. The first group generates a stream of documents with one document per term and category:

 { $group : { 
      _id :  { 
        category: "$category",
        term: "$term",
      },
      total: { $sum : 1 } 
   }
 }

A second group will then merge all documents with the same term into one, using the $push operator to merge the categories into an array:

 { $group : { 
      _id :  "$_id.category",
      terms: { 
          $push: { 
              term:"$_id.term",
              total:"$total"
          }
      }
   }
 }

Answer 2

Query:

    db.getCollection('orders').aggregate([
    {$match:{
        tipo: {$regex:"[A-Z]+"}
        }
    },
    {$group:
        { 
            _id:{
                codigo:"1",
                tipo:"$tipo",
            },
            total:{$sum:1}
        }
    },
    {$group:
        {
            _id:"$_id.codigo",
            tipos:
            {
                $push:
                {
                    tipo:"$_id.tipo",
                    total:"$total"
                }
            },
            totalGeneral:{$sum:"$total"}

        }

    }


]);

Response:

{
"_id" : "1",
"tipos" : [ 
    {
        "tipo" : "TIPO_01",
        "total" : 13.0
    }, 
    {
        "tipo" : "TIPO_02",
        "total" : 2479.0
    }, 
    {
        "tipo" : "TIPO_03",
        "total" : 12445.0
    }, 
    {
        "tipo" : "TIPO_04",
        "total" : 12445.0
    }, 
    {
        "tipo" : "TIPO_05",
        "total" : 21.0
    }, 
    {
        "tipo" : "TIPO_06",
        "total" : 21590.0
    }, 
    {
        "tipo" : "TIPO_07",
        "total" : 1065.0
    }, 
    {
        "tipo" : "TIPO_08",
        "total" : 562.0
    }
],
"totalGeneral" : 50620.0

}