I'm trying to write a Mongoose aggregation query to get the sum of a field for all matching documents.

Meaning I have a model that looks like:

{
    itemNumber: String,
    quantity: Number

}

There are multiple documents with the same itemNumber, I'm looking to get the sum of the quantity fields.

What's the easiest way to do this?

CodePudding user response：

use group

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

mongoplayground