Mongoose get all elements in array of multiple documents

Question

I have a Schema Classroom with properties:
_id
studentEmails (array of Strings. Each student has an unique email)

I am given an array of Classroom ids, and I want to find every student email that belongs one of those classrooms, without duplicates. How do I do this? I was thinking I could get every student email and then remove duplicates later, but I would much rather do it through mongoose.

For example, if I had the following classrooms:

_id: 1
studentEmails: ["[email protected]", "[email protected]"]

_id: 2
studentEmails: ["[email protected]", "[email protected]"]

And the following query parameter:

[1, 2]

I want to get [[email protected], [email protected], [email protected]]. The _id is a mongoose ObjectId, but simplified in the example.

you can use in, here is sample p.find() .where("studentEmails") .in([1, 2]) — Nonik
– Nonik, Commented Oct 22, 2020 at 23:20

vishnu · Accepted Answer · 2020-10-23 02:49:27Z

1

You can use the distinct method with condition for this.

Model.distinct(
  "studentEmails",
  { _id: { $in: [mongoose.Types.ObjectId("1"), mongoose.Types.ObjectId("2")] } },
  function (err, data) {
    if (err) {
      console.log(err);
    } else {
      console.log(data);
    }
  }
);

answered Oct 23, 2020 at 2:49

vishnu

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