Projection: choosing fields

A projection is the second argument to find(), and it decides which fields come back. Two rules cover almost everything: you cannot mix inclusion and exclusion in one projection, and _id is included unless you explicitly turn it off.

Suppose the document contains:

{
  _id: 1,
  name: "Denish",
  email: "denish@example.com",
  passwordHash: "secret",
  address: {...}
}

You probably don’t want everything.

db.users.find(
  {
    status: "active"
  },
  {
    name: 1,
    email: 1
  }
)

Result:

{
  _id: 1,
  name: "Denish",
  email: "denish@example.com"
}

_id is included by default.

Exclude it:

db.users.find(
  {},
  {
    _id: 0,
    name: 1,
    email: 1
  }
)

Exclusion projection

db.users.find(
  {},
  {
    passwordHash: 0,
    internalNotes: 0
  }
)

Generally, you don’t mix inclusion and exclusion in the same projection, except _id.