query in mongo db - sql

Question

my friend is telling me that mongo is not worth learning since its very bad to do complex querying, something like this:
SELECT person, SUM(score), AVG(score), MIN(score), MAX(score), COUNT(*)
FROM demo
WHERE score > 0 AND person IN('bob','jake')
GROUP BY person;
he is telling me that if i want to do this query with mongo i have to write this
db.demo.group({
"key": {
"person": true
},
"initial": {
"sumscore": 0,
"sumforaverageaveragescore": 0,
"countforaverageaveragescore": 0,
"countstar": 0
},
"reduce": function(obj, prev) {
prev.sumscore = prev.sumscore + obj.score - 0;
prev.sumforaverageaveragescore += obj.score;
prev.countforaverageaveragescore++;
prev.minimumvaluescore = isNaN(prev.minimumvaluescore) ? obj.score : Math.min(prev.minimumvaluescore, obj.score);
prev.maximumvaluescore = isNaN(prev.maximumvaluescore) ? obj.score : Math.max(prev.maximumvaluescore, obj.score);
if (true != null) if (true instanceof Array) prev.countstar += true.length;
else prev.countstar++;
},
"finalize": function(prev) {
prev.averagescore = prev.sumforaverageaveragescore / prev.countforaverageaveragescore;
delete prev.sumforaverageaveragescore;
delete prev.countforaverageaveragescore;
},
"cond": {
"score": {
"$gt": 0
},
"person": {
"$in": ["bob", "jake"]
}
}
});
so having no mongodb background i dont know what to think and i've been searching arround and everyone says that mongo is better for a lot of stuff, still how do i do this query in mongo?
is it like my friend says? or is there a easier way to do this?

Answer 1

There is a much easier way to do that.
db.demo.aggregate([
{ $match: { score: { $gt: 0 }, person: { $in: ["bob", "jake"] } } },
{ $group: { _id: "$person", scoreSum: { $sum: "$score" }, scoreAvg: { $avg: "$score" }, scoreMin: { $min: "$score" }, scoreMax: { $max: "$score" }, count: { $sum: 1 } } }
])