MongoDB SELECT COUNT GROUP BY

Question

I am playing around with MongoDB trying to figure out how to do a simple

SELECT province, COUNT(*) FROM contest GROUP BY province

But I can't seem to figure it out using the aggregate function. I can do it using some really weird group syntax

db.user.group({ 

"key": { 

"province": true 

}, 

"initial": { 

"count": 0 

}, 

"reduce": function(obj, prev) { 

if (true != null) if (true instanceof Array) prev.count += true.length; 

else prev.count++; 

} 

});

But is there an easier/faster way using the aggregate function?

Answer 1

In MongoDB group by can be used by using below-mentioned code:-

db.contest.aggregate([ 

{"$group" : {_id:"$province", count:{$sum:1}}} 

])

Answer 2

If you need multiple columns to group by, follow the following model:

  db.BusinessProcess.aggregate({

    "$group": {

        _id: {

            status: "$status",

            type: "$type"

        },

        count: {

            $sum: 1

        }

    }

   })