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Display only an element found in an array in MongoDB?
To display only an element found in an array, use aggregate(). Let us create a collection with documents −
> db.demo204.insertOne(
... {
... "_id" : 101,
... "Name" : "Chris",
... "Age" : 23,
... "details" : [
... {
... "id" : "1001",
... "empId" : "John_1001",
... "salary" : "50000",
... "Technology" : "Java"
... },
... {
... "id" : "1002",
... "empId" : "John_1002"
... },
... {
... "id" : "1003",
... "empId" : "John_10003",
... "salary" : "60000",
... "Technology" : "MongoDB"
... }
... ]
... }
...);
{ "acknowledged" : true, "insertedId" : 101 }Display all documents from a collection with the help of find() method −
> db.demo204.find();
This will produce the following output −
{
"_id" : 101, "Name" : "Chris", "Age" : 23, "details" : [
{ "id" : "1001", "empId" : "John_1001", "salary" : "50000", "Technology" : "Java" },
{ "id" : "1002", "empId" : "John_1002" },
{ "id" : "1003", "empId" : "John_10003", "salary" : "60000", "Technology" : "MongoDB" }
]
}Following is the query to display only an element found in an array in MongoDB −
> db.demo204.aggregate(
... [
... { "$match": { "details.id": "1001" }},
... { "$unwind": "$details" },
... { "$match": { "details.id":"1001" }},
... { "$project": { "Technology": "$details.Technology", "_id":0 }}
... ]
...)This will produce the following output −
{ "Technology" : "Java" }
Updated on: 27-Mar-2020
240 Views
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