MongoDB nested group?

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"          }      }   } }

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

}