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

stackoverflow.com/questions/4057196/…
– Ebubekir Dirican
Commented Dec 19, 2012 at 15:41 — Ebubekir Dirican, Commented Dec 19, 2012 at 15:41

ltfishie · Accepted Answer · 2012-12-19 15:33:56Z

5

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

answered Dec 19, 2012 at 15:33

ltfishie

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+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
Commented Dec 19, 2012 at 15:38

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Sushant Gupta · Accepted Answer · 2012-12-19 15:34:45Z

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, 2012 at 15:34

Sushant Gupta

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slownage · Accepted Answer · 2012-12-19 15:33:54Z

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, 2012 at 15:33

slownage

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I think this matches documents with no firstName as well; not what the OP is asking for.
– paulmelnikow
Commented Dec 19, 2012 at 15:38

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Oleg V. Volkov · Accepted Answer · 2012-12-19 15:34:10Z

0

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

answered Dec 19, 2012 at 15:34

Oleg V. Volkov

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But it would find fields where firstName doesn't even exist.
– Sushant Gupta
Commented Dec 19, 2012 at 15:35
1

Indeed. I've just upvoted answer with link to FAQ which cover all of possibilities.
– Oleg V. Volkov
Commented Dec 19, 2012 at 15:37
Yup, very nice and elegant solution. I liked it :)
– Sushant Gupta
Commented Dec 19, 2012 at 15:38

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4 Answers 4