//定义一个Sum的函数

db.system.js.save({_id:"Sum",

            value:function(key,values)

            {

                var total = ;

                for(var i =;i <values.length;i++)

                    total += values[i];

                return total;

                }});

//使用Sum函数

db.loadServerScripts();Sum(,[,,,,,,,,])

//在People集合中使用Sum函数

db.people.runCommand(

{

    mapreduce :"people",

    map:function(){

            emit(

            {key0:this.name,

            key1:this.created},

            this.phonenum

            );},

        reduce:function(key,values)

        {

            var result = Sum(key, values);

            return result;

            },

        out :{inline :  }});