I'm new to MongoDb, I have the same problem that Stennie describes. I tried to query this document in Compass:
{
"_id": 1,
"name": {
"first": "John",
"last": "Backus"
},
"birth": {
"$date": "1924-12-02T23:00:00.000Z"
},
"death": {
"$date": "2007-03-16T23:00:00.000Z"
},
"contribs": ["Fortran", "ALGOL", "Backus-Naur Form", "FP"],
"awards": [{
"award": "National Medal",
"year": 1975,
"by": "NSF"
}, {
"award": "Turing Award",
"year": 1977,
"by": "ACM"
}]
}
When to run this query:{awards: {$elemMatch: {award:'National Medal', year:1975}}}
for this single document, I get the same result:
{
"_id": 1,
"name": {
"first": "John",
"last": "Backus"
},
"birth": {
"$date": "1924-12-02T23:00:00.000Z"
},
"death": {
"$date": "2007-03-16T23:00:00.000Z"
},
"contribs": ["Fortran", "ALGOL", "Backus-Naur Form", "FP"],
"awards": [{
"award": "National Medal",
"year": 1975,
"by": "NSF"
}, {
"award": "Turing Award",
"year": 1977,
"by": "ACM"
}]
}
It is possible to obtain the single element searched for in this way:
{
"_id": 1,
"name": {
"first": "John",
"last": "Backus"
},
"birth": {
"$date": "1924-12-02T23:00:00.000Z"
},
"death": {
"$date": "2007-03-16T23:00:00.000Z"
},
"contribs": ["Fortran", "ALGOL", "Backus-Naur Form", "FP"],
"awards": [{
"award": "National Medal",
"year": 1975,
"by": "NSF"
}, {}]
Thank you
Docs Home → MongoDB Manual
On this page
- Query for a Document Nested in an Array
- Specify a Query Condition on a Field in an Array of Documents
- Specify Multiple Conditions for Array of Documents
- Additional Query Tutorials
➤ Use the Select your language drop-down menu in the upper-right to set the language of the following examples.
The following example selects all documents where an element in the instock
array matches the specified document:
Equality matches on the whole
embedded/nested document require an exact match of the specified document, including the field order. For example, the following query does not match any documents in the inventory
collection:
If you do not know the index position of the document nested in the array, concatenate the name of the array field, with a dot [.
] and the name of the field in the nested document.
The following example selects all documents where the instock
array
has at least one embedded document that contains the field qty
whose value is less than or equal to 20
:
Using dot notation, you can specify query conditions for field in a document at a particular index or position of the array. The array uses zero-based indexing.
Note
When querying using dot notation, the field and index must be inside quotation marks.
The following example selects all documents where the instock
array has as its first element a document that contains the field qty
whose value is less than or equal to 20
:
When specifying conditions on more than one field nested in an array of documents, you can specify the query such that either a single document meets these condition or any combination of documents [including a single document] in the array meets the conditions.
Use $elemMatch
operator to specify multiple criteria on an array of embedded documents such that at least one embedded document satisfies all the specified criteria.
The following example queries for documents where the instock
array has at least one embedded document that contains both the field
qty
equal to 5
and the field warehouse
equal to A
:
The following example queries for documents where the instock
array has at least one embedded document that contains the field qty
that is greater than 10
and less than or equal to 20
:
If the compound query conditions on an array field do not use the
$elemMatch
operator, the query selects those documents whose array contains any combination of elements that satisfies the conditions.
For example, the following query matches documents where any document nested in the instock
array has the qty
field greater than 10
and any document [but not necessarily the same embedded document] in the
array has the qty
field less than or equal to 20
:
The following example queries for documents where the instock
array has at least one embedded document that contains the field qty
equal to 5
and at least one embedded document [but not necessarily the same embedded document] that contains the field warehouse
equal to A
:
For additional query examples, see:
Query an Array
Query Documents
Query on Embedded/Nested Documents