Mongo DB，计数文档

Question

Is there a way to query mongoDB in order to get counted documents with certain date? As for example, I have documents:

[{
fullDate: '2020/02/01',
someData: 'someData',
},
{
fullDate: '2020/03/01',
someData: 'someData',
},
{
fullDate: '2020/03/01',
someData: 'someData',
},
{
fullDate: '2020/02/01',
someData: 'someData',
},
{
fullDate: '2020/02/01',
someData: 'someData',
},
{
fullDate: '2020/02/01',
someData: 'someData',
}]

I would like to make counting query to get info that there are 4 documents with fullDate of 2020/02/01 and 2 documents with fullDate of 2020/02/03 in one query. Thank you!

Answer 1

Sounds like you need a simple $group stage.

db.collection.aggregate([
    {
        $group: {
            _id: "$fullDate",
            count: {$sum: 1}
        }
    }
])