Question

Hi im newbie into MongoDB and im needing to translate this sql query to mongodb using two techniques first in MapReduce method and other Aggregation method. Someone may help?

select
    sum(l_extendedprice*l_discount) as revenue
from 
    lineitem
where 
    l_shipdate >= date '1994-01-01'
    and l_shipdate < date '1994-01-01' + interval '1' year
    and l_discount between 0.06 - 0.01 and 0.06 + 0.01
    and l_quantity < 24;

Answer 1

http://www.mongodb.org/display/DOCS/MapReduce

For your sample, using map/reduce

var m = function () { emit(1, {this.l_extendedprice * this.l_discount})};

var r = function (k, vals) {
    var sum = 0;
    for (var i = 0; i < vals.length; i++) {
       sum += vals[i];
    }
    return sum;
}

var res = db.stuff.mapReduce(m, r,  {
                            out:"stuff_aggr",
                            query: { 
                                "l_shipdate": {$gte:  ISODate("1994-01-01T00:00:00.000Z")}, 
                                "l_shipdate": {$lte:  ISODate("1995-01-01T00:00:00.000Z")},
                                "l_discount": {$gte: 0.05}, 
                                "l_discount": {$lte: 0.07}, 
                                "l_quantity": {$lt: 24}
                            }
});

Aggregation is still a beta feature. MapReduce is still the better option. Am assuming you wanted to see if a complex where clause can be handled easily… Its not that different from SQL as long as you are restricting yourself to one collection/table.