Mongodb group and sort

Question

How can I translate the following Sql query for Mongo?:

select a,b,sum(c) csum from coll wh         


        

Answer 1

Using the aggregate framework, you can do the following:

db.coll.aggregate({ 
    $group: { 
        _id: "$a", 
        countA: { $sum: 1}, 
        sumC:{ $sum: "$c"}, 
    },
    $sort:{a:1}
});

However, if you have too much data you may get the following error message:

{
    "errmsg" : "exception: aggregation result exceeds maximum document size (16MB)",
    "code" : 16389,
    "ok" : 0
}

See more about SQL to Mongo translation here: http://docs.mongodb.org/manual/reference/sql-aggregation-comparison/