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" }