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How to perform intersection of sets between the documents in a single collection in MongoDB?
You can use $setIntersection for this. Let us first create a collection with documents −
> db.setInterSectionDemo.insertOne(
... {"_id":101, "Value1":[55,67,89]}
... );
{ "acknowledged" : true, "insertedId" : 101 }
> db.setInterSectionDemo.insertOne(
... {"_id":102, "Value2":[90,45,55]}
... );
{ "acknowledged" : true, "insertedId" : 102 }
> db.setInterSectionDemo.insertOne(
... {"_id":103, "Value3":[92,67,45]}
... );
{ "acknowledged" : true, "insertedId" : 103 }Following is the query to display all documents from a collection with the help of find() method −
> db.setInterSectionDemo.find().pretty();
This will produce the following output −
{ "_id" : 101, "Value1" : [ 55, 67, 89 ] }
{ "_id" : 102, "Value2" : [ 90, 45, 55 ] }
{ "_id" : 103, "Value3" : [ 92, 67, 45 ]Here is the query to find intersection of sets between the documents in a single collection in MongoDB −
> db.setInterSectionDemo.aggregate([
... {
... "$match": {
... "_id": { "$in": [101, 103] }
... }
... },
... {
... "$group": {
... "_id": 0,
... "firstValue": { "$first": "$Value1" },
... "secondValue": { "$last": "$Value3" }
... }
... },
... {
... "$project": {
... "firstValue": 1,
... "secondValue": 1,
... "CommonValue": { "$setIntersection": [ "$firstValue", "$secondValue" ] },
... "_id": 0
... }
... }
... ]);This will produce the following output −
{ "firstValue" : [ 55, 67, 89 ], "secondValue" : [ 92, 67, 45 ], "CommonValue" : [ 67 ] }
Updated on: 30-Jul-2019
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