MongoDB: How to query for records where field is null or not set?

Question

I have an Email document which has a sent_at date field:

{
  \'sent_at\': Date( 1336776254000 )
}

If this E

Answer 1

Use:

db.emails.count({sent_at: null})

Which counts all emails whose sent_at property is null or is not set. The above query is same as below.

db.emails.count($or: [
  {sent_at: {$exists: false}},
  {sent_at: null}
])

Answer 2

You can also try this:

db.emails.find($and:[{sent_at:{$exists:true},'sent_at':null}]).count()

Answer 3

If you want to ONLY count the documents with sent_at defined with a value of null (don't count the documents with sent_at not set):

db.emails.count({sent_at: { $type: 10 }})

Answer 4

db.employe.find({ $and:[ {"dept":{ $exists:false }, "empno": { $in:[101,102] } } ] }).count();

Answer 5

Seems you can just do single line:

{ "sent_at": null }

Answer 6

If the sent_at field is not there when its not set then:

db.emails.count({sent_at: {$exists: false}})

If its there and null, or not there at all:

db.emails.count({sent_at: null})

Refer here for querying and null