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How to filter array elements in MongoDB?
You can use $setIntersection operator along with aggregate framework to filter array elements in MongoDB. Let us first create a collection with documents −
> db.filterArrayElementsDemo.insertOne( { "Scores": [10,45,67,78,90,98,99,92] } );
{
"acknowledged" : true,
"insertedId" : ObjectId("5cd2d582b64f4b851c3a13c8")
}Following is the query to display all documents from a collection with the help of find() method −
> db.filterArrayElementsDemo.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5cd2d582b64f4b851c3a13c8"),
"Scores" : [
10,
45,
67,
78,
90,
98,
99,
92
]
}Following is the query to filter array elements −
> db.filterArrayElementsDemo.aggregate([
... { $match : {
... _id: ObjectId("5cd2d582b64f4b851c3a13c8")
... }},
... { $project: {
... Scores: {
... $setIntersection: ['$Scores', [10,98,99]]
... }
... }}
... ]);This will produce the following output −
{ "_id" : ObjectId("5cd2d582b64f4b851c3a13c8"), "Scores" : [ 10, 98, 99 ] }
Updated on: 30-Jul-2019
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