How to query nested objects?
Solution 1
db.messages.find( { headers : { From: "[email protected]" } } )
This queries for documents where headers
equals { From: ... }
, i.e. contains no other fields.
db.messages.find( { 'headers.From': "[email protected]" } )
This only looks at the headers.From
field, not affected by other fields contained in, or missing from, headers
.
Solution 2
Since there is a lot of confusion about queries MongoDB collection with sub-documents, I thought its worth to explain the above answers with examples:
First I have inserted only two objects in the collection namely: message
as:
> db.messages.find().pretty()
{
"_id" : ObjectId("5cce8e417d2e7b3fe9c93c32"),
"headers" : {
"From" : "[email protected]"
}
}
{
"_id" : ObjectId("5cce8eb97d2e7b3fe9c93c33"),
"headers" : {
"From" : "[email protected]",
"To" : "[email protected]"
}
}
>
So what is the result of query:
db.messages.find({headers: {From: "[email protected]"} }).count()
It should be one because these queries for documents where headers
equal to the object {From: "[email protected]"}
, only i.e. contains no other fields or we should specify the entire sub-document as the value of a field.
So as per the answer from @Edmondo1984
Equality matches within sub-documents select documents if the subdocument matches exactly the specified sub-document, including the field order.
From the above statements, what is the below query result should be?
> db.messages.find({headers: {To: "[email protected]", From: "[email protected]"} }).count()
0
And what if we will change the order of From
and To
i.e same as sub-documents of second documents?
> db.messages.find({headers: {From: "[email protected]", To: "[email protected]"} }).count()
1
so, it matches exactly the specified sub-document, including the field order.
For using dot operator, I think it is very clear for every one. Let's see the result of below query:
> db.messages.find( { 'headers.From': "[email protected]" } ).count()
2
I hope these explanations with the above example will make someone more clarity on find query with sub-documents.
Solution 3
The two query mechanism work in different ways, as suggested in the docs at the section Subdocuments:
When the field holds an embedded document (i.e, subdocument), you can either specify the entire subdocument as the value of a field, or “reach into” the subdocument using dot notation, to specify values for individual fields in the subdocument:
Equality matches within subdocuments select documents if the subdocument matches exactly the specified subdocument, including the field order.
In the following example, the query matches all documents where the value of the field producer is a subdocument that contains only the field company
with the value 'ABC123'
and the field address
with the value '123 Street'
, in the exact order:
db.inventory.find( {
producer: {
company: 'ABC123',
address: '123 Street'
}
});
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Edmondo
Updated on July 08, 2022Comments
-
Edmondo almost 2 years
I have a problem when querying mongoDB with nested objects notation:
db.messages.find( { headers : { From: "[email protected]" } } ).count() 0 db.messages.find( { 'headers.From': "[email protected]" } ).count() 5
I can't see what I am doing wrong. I am expecting nested object notation to return the same result as the dot notation query. Where am I wrong?
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trysis about 10 yearsIs there any way of doing this without the quotes around "headers.From"?
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trysis about 10 yearsI don't know, just wondering, and thought it may sometimes be useful.
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Ryan Wheale almost 10 years@trysis - In practice, I have found that declaring inline objects (like the examples in mongo[ose] docs, and in most examples out there) simply isn't enough in the real world. I have developed the habit of creating 'conditions' and 'fields' objects on which I can do stuff like
conditions['some.path'] = 'value'
in my business logic, then run a single query at the end:find(conditions, fields, callback);
-
Capaj over 8 yearsI was going crazy. This seems to me quite inconsistent, because when querying objects it's direct properties can be matched in any order.
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Rens Tillmann almost 4 yearsWhat if let's say I have a key which contains "domain.com", this will not work:
domains.domain.com
. Is there any workaround for this scenario (without altering the domain.com to something else e.g domain_com)? -
Rens Tillmann almost 4 yearsAnswering my own comment, it's best to avoid using dots completely in your keys. In my solution I completely ditched the domains being keys, and created a slice/array instead.