Today in this article, we will see how to MongoDB-Query deeply nested array containing a specific value. Show
Today in this article, we will cover below aspects, We will cover below a few specific scenarios like dealing with [] array type elements,
Sample schema as below,  In the above example, we have two nested arrays Example Books [] and Category []. MongoDB – Find document from Nested array elementCommand Nested 3 array pattern, { <array-field1>.<array-field2>.<array-field3>.<Field-Name>: {<value> }The below example shows an array filter where we get the list of documents where the value of a nested array element i.e category [] is equal to the value specified. {'Books.category.key': 'test2-1'}Example MongoDB – Find documents by nested array lengthCommand { <array-field1>.<array-field2: {$size :<size-specified> }Example The below example shows an array filter where we get the list of documents based on array size i.e category [] size is equal to the size specified. {'Books.category': {$size:2}}
MongoDB – Find a document with a nested array by specifying multiple conditionsExample MongoDB query array with fields that contains a given string, {'Books.category.key': {$regex: '-'}}Above query returns records where array element “Key” attribute has a value that matches or contains “-“. You are asked to filter on this column. If this field would have carried dictionaries, then the query for applying the filter would have been comparatively easier. However, this is not the case. To achieve this, you need to unwind this column and apply the match operator. The $unwind OperatorBy using the The below code will apply a filter on a collection ‘ The query below: SQL db.getCollection('ProductMaster') .aggregate( {$unwind: '$categories'}, {$match: {"categories": {$in: ['Beauty']}}} ); Points of InterestThis morning, I got into a wierd kind of a scenario where I had to apply the filter on an array inside another array. The filter on a LicenseThis article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL) Written By Pankaj Jha
This member has not yet provided a Biography. Assume it's interesting and varied, and probably something to do with programming. To set filtering conditions, use $filter and $cond in MongoDB aggregate(). The $filter selects a subset of an array to return based on the specified condition. Let us create a collection with documents − > db.demo725.insertOne(
... {
...
... "details": {
...
... "userMessages": [
... {
... "Messages": [
... { "Message": "Hello" },
... { "Message": "How" },
... { "Message": "are" }
... ]
...
... },
... {
... "Messages": [
... { "Message": "Good" },
... { "Message": "Bye" }
...
... ]
... },
... {
... "Messages": [
... { "Message": "Hello" },
... { "Message": "Bye" }
...
... ]
...
... }
... ]
... }
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5eab16cd43417811278f5893")
}Display all documents from a collection with the help of find() method − > db.demo725.find(); This will produce the following output − { "_id" : ObjectId("5eab16cd43417811278f5893"), "details" : { "userMessages" : [ { "Messages" : [ { "Message" : "Hello" }, { "Message" : "How" }, { "Message" : "are" } ] }, { "Messages" : [ { "Message" : "Good" }, { "Message" : "Bye" } ] }, { "Messages" : [ { "Message" : "Hello" }, { "Message" : "Bye" } ] } ] } }Following is the query to set filtering conditions for nested array − > db.demo725.aggregate([
... {
... $addFields: {
... "details.userMessages": {
... $filter: {
... input: "$details.userMessages",
... as: "out",
... cond: {
... $anyElementTrue: {
... $map: {
... input: "$$out.Messages",
... in: { $gte: [ { $indexOfBytes: [ "$$this.Message", "Hello" ] }, 0 ] }
... }
... }
... }
... }
... }
... }
... }
... ]).pretty()This will produce the following output − {
"_id" : ObjectId("5eab16cd43417811278f5893"),
"details" : {
"userMessages" : [
{
"Messages" : [
{
"Message" : "Hello"
},
{
"Message" : "How"
},
{
"Message" : "are"
}
]
},
{
"Messages" : [
{
"Message" : "Hello"
},
{
"Message" : "Bye"
}
]
}
]
}
}How to filter an array in MongoDB?Filter MongoDB Array Element Using $Filter Operator
This operator uses three variables: input – This represents the array that we want to extract. cond – This represents the set of conditions that must be met. as – This optional field contains a name for the variable that represent each element of the input array.
How do I search inside an array in MongoDB?To query if the array field contains at least one element with the specified value, use the filter { <field>: <value> } where <value> is the element value. To specify conditions on the elements in the array field, use query operators in the query filter document: { <array field>: { <operator1>: <value1>, ... } }
How to query nested fields in MongoDB?In MongoDB, you can access the fields of nested/embedded documents of the collection using dot notation and when you are using dot notation, then the field and the nested field must be inside the quotation marks. Document: three documents that contain the details of the students in the form of field-value pairs.
What is $filter in MongoDB?Definition. $filter. Selects a subset of an array to return based on the specified condition. Returns an array with only those elements that match the condition. The returned elements are in the original order.
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Filter nested array MongoDB C#
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