您如何在Mongo中计算最大和唯一性？

Question

I have a bunch of documents:

{ "name" : "A", "value" : 10},
{ "name" : "B", "value" : 12},
{ "name" : "B", "value" : 14},
{ "name" : "A", "value" : 16},
{ "name" : "C", "value" : 11}

I want to find the minimum value for each name, so the result would be

{ "name" : "A", "value" : 10},
{ "name" : "B", "value" : 12},
{ "name" : "C", "value" : 11}

What is the correct way to do this query in Mongo? I keep thinking in terms of SQL.

Answer 1

For the minimum, you can do this by using Mongo's Aggregation Framework with " $group " and "$min". Assuming that you had a collection named "myCollection," you could try something like this:

db.myCollection.aggregate({$group:{_id:"$name", minimumValue: {$min : "$value"}}});