Template
single collection
multiple collections
mgodatagen
update
indexe
explain
Stage
Database
bson
mgodatagen
[{"item":1,status:"active"},{"item":2,status:"unactive"}]
Query
db.collection.aggregate({$group:{_id:"$item","active":{$sum:{$cond:[{$eq:["$status","active"]},1,0]}}}})
Result