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MongoDB aggregation to fetch documents with specific field value?
For this, use aggregate(). Let’s say we have to fetch documents with a field “Age” with value “21”.
Let us now create a collection with documents −
> db.demo685.insertOne(
... {
... "details":
... [
... {
... Name:"Chris",
... Age:21
... },
... {
... Name:"David",
... Age:23
... },
... {
... Name:"Bob",
... Age:21
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5ea54f6fa7e81adc6a0b395b")
}
Display all documents from a collection with the help of find() method −
> db.demo685.find();
This will produce the following output −
{ "_id" : ObjectId("5ea54f6fa7e81adc6a0b395b"), "details" : [
{ "Name" : "Chris", "Age" : 21 },
{ "Name" : "David", "Age" : 23 },
{ "Name" : "Bob", "Age" : 21 }
] }
Following is the query for MongoDB aggregation −
> db.demo685.aggregate([ { $unwind: "$details" }, { $match: { "details.Age": 21 } }, { $project: {_id: 0}} ]).pretty();
This will produce the following output −
{ "details" : { "Name" : "Chris", "Age" : 21 } }
{ "details" : { "Name" : "Bob", "Age" : 21 } }
Updated on: 2020-05-14T09:03:57+05:30
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