How to use dot in field name?

Question

How to use dot in field name ?

I see error in example:

db.test2.insert({ "a.a" : "b" })  can't have . in field names [a.a] 

Answer 1

You can replace dot symbols of your field name to Unicode equivalent of \uff0E

db.test.insert({"field\uff0ename": "test"}) db.test.find({"field\uff0ename": "test"}).forEach(printjson) { "_id" : ObjectId("5193c053e1cc0fd8a5ea413d"), "field．name" : "test" } 

See more:

1. http://docs.mongodb.org/manual/faq/developers/#faq-dollar-sign-escaping
2. http://docs.mongodb.org/manual/core/document/#dot-notation

Answer 2

Actualy you may use dots in queries. See: http://www.mongodb.org/display/DOCS/Dot+Notation+%28Reaching+into+Objects%29

Because of this special dot symbol mean you cannot use it in field names. Like you cannot use dot symbol in identifiers in most of programming languages.

You may write query db.test2.find({ "a.a" : "b" }) but if you want to be able to write such a query you need to insert your object like so: db.test2.insert({"a": {"a": "b"}}). This will create document with the field named "a" with the value of embeded document containing the field named "a" (again) with the value "b".