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

db.coll.group(
       {key: { a:true, b:true },
        cond: { active:1 },
        reduce: function(obj,prev) { prev.csum += obj.c; },
        initial: { csum: 0 }
        });

You can execute it in MongoDB