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Query to retrieve multiple items in an array in MongoDB?
To retrieve multiple items in an array, use aggregate framework. Let us first create a collection with documents −
> db.retrieveMultipleDemo.insertOne(
... {
... "UserDetails":
... [
... { "_id": "101", "UserName":"John", "UserAge": 23 },
... { "_id": "102", "UserName":"Carol", "UserAge": 21 },
... { "_id": "103", "UserName":"David", "UserAge": 23},
... { "_id": "104", "UserName":"Sam", "UserAge": 25}
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd40c85edc6604c74817cf0")
}Following is the query to display all documents from a collection with the help of find() method −
> db.retrieveMultipleDemo.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5cd40c85edc6604c74817cf0"),
"UserDetails" : [
{
"_id" : "101",
"UserName" : "John",
"UserAge" : 23
},
{
"_id" : "102",
"UserName" : "Carol",
"UserAge" : 21
},
{
"_id" : "103",
"UserName" : "David",
"UserAge" : 23
},
{
"_id" : "104",
"UserName" : "Sam",
"UserAge" : 25
}
]
}Following is the query to retrieve multiple items in an array −
> db.retrieveMultipleDemo.aggregate([
... {$unwind:"$UserDetails"},
... {$match:{"UserDetails._id":{$in:myIds},"UserDetails.UserAge":23}},
... {$group:{"_id":"_id","UserDetails":{$push:"$UserDetails"}}},
... {$project:{"_id":0,"UserDetails":1}}
... ]);This will produce the following output −
{ "UserDetails" : [ { "_id" : "101", "UserName" : "John", "UserAge" : 23 }, { "_id" : "103", "UserName" : "David", "UserAge" : 23 } ] }
Updated on: 30-Jul-2019
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