MongoDB equal to

Question

I'm trying to run a MongoDB query and return those records where a field is null (more specifically None in pyMongo). So it has to be equal to null.

I know this is not equal to:

{"firstName": {"$ne": None }}

I can't find the equal operator in the documentation.

Thanks

http://stackoverflow.com/questions/4057196/how-do-you-query-this-in-mongo-is-not-null — Ebubekir Dirican, Dec 19 '12 at 15:41

score 5 · Accepted Answer · answered Dec 19 '12 at 15:33

5

{"firstName":{ $type: 10 } } should give you what you want

answered Dec 19 '12 at 15:33

ltfishie

+1 not for the answer, but for the link that covers all possibilities. It'd be good to have concise version of it summarized in answer directly. – Oleg V. Volkov Dec 19 '12 at 15:38

score 2 · Answer 2 · answered Dec 19 '12 at 15:34

2

If you want to find records having firstName defined in record with value None defined:

db.testcoll.find({$and: [{"firstName": None}, {"firstName": {$exists: true}}]})

answered Dec 19 '12 at 15:34

Sushant Gupta

score 1 · Answer 3 · answered Dec 19 '12 at 15:33

1

If I understand correctly it should be just:

{"firstName": None}

With yours you are getting all the documents that have a value different of None. {"firstName": {"$ne": None }}

answered Dec 19 '12 at 15:33

slownage

I think this matches documents with no `firstName` as well; not what the OP is asking for. – paulmelnikow Dec 19 '12 at 15:38

score 0 · Answer 4 · answered Dec 19 '12 at 15:34

0

Use {"firstName": { "$exists": false }} to find records where there's no such field.

answered Dec 19 '12 at 15:34

Oleg V. Volkov

But it would find fields where firstName doesn't even exist. – Sushant Gupta Dec 19 '12 at 15:35
1

Indeed. I've just upvoted answer with link to FAQ which cover all of possibilities. – Oleg V. Volkov Dec 19 '12 at 15:37
Yup, very nice and elegant solution. I liked it :) – Sushant Gupta Dec 19 '12 at 15:38

4 Answers4