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MongoDB query to exclude if id is equal to a document field array value
For this, use $not along with $in. Let us create a collection with documents −
[ { id: "101", subjectid: [ "102" ] }, { id: "102", subjectid: [ "102" ] } ]
Here is the snapshot.
Display all documents from a collection with the help of find() method −
db.collection.find()
This will produce the following output −
[ { "_id": ObjectId("5a934e000102030405000000"), "id": "101", "subjectid": [ "102" ] }, { "_id": ObjectId("5a934e000102030405000001"), "id": "102", "subjectid": [ "102" ] } ]
Following is the query that uses $expr, $not and $in to fetch values excluding matching field array value −
db.collection.find({ $expr: { $not:{ $in: [ "$id", "$subjectid" ] } } })
This will produce the following output −
[ { "_id": ObjectId("5a934e000102030405000000"), "id": "101", "subjectid": [ "102" ] } ]
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