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How to get a particular element from MongoDB array?
You can use the aggregate framework to get a particular element from the MongoDB array. To understand the concept, let us create a collection with the document. The query to create a collection with the document is as follows −
> db.getParticularElement.insertOne({"InstructorName":"Larry","InstructorTechnicalSubject":["Java","C","C++","MongoDB","MySQL","SQL Server"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c7ee027559dd2396bcfbfb1")
}Display all documents from a collection with the help of find() method. The query is as follows −
> db.getParticularElement.find().pretty();
The following is the output −
{
"_id" : ObjectId("5c7ee027559dd2396bcfbfb1"),
"InstructorName" : "Larry",
"InstructorTechnicalSubject" : [
"Java",
"C",
"C++",
"MongoDB",
"MySQL",
"SQL Server"
]
}Here is the query to get a particular element from an array −
> db.getParticularElement.aggregate([
... {
... $project:
... {
... ElementFromAnArray: 1,
... FourthElement: { $arrayElemAt: [ "$InstructorTechnicalSubject", 3] },
...
... }
... }
... ]);The following is the output −
{ "_id" : ObjectId("5c7ee027559dd2396bcfbfb1"), "FourthElement" : "MongoDB" }
Updated on: 30-Jul-2019
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