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Display a value with $addToSet in MongoDB with no duplicate elements?
Use $addToSet operator to ensures that there are no duplicate items added to the set. Let us first create a collection with documents −
> db.getDistinctDemo.insertOne({"Values":[100,200]}); { "acknowledged" : true, "insertedId" : ObjectId("5cef69f9ef71edecf6a1f69d") } > db.getDistinctDemo.insertOne({"Values":[300,100]}); { "acknowledged" : true, "insertedId" : ObjectId("5cef6a07ef71edecf6a1f69e") }
Display all documents from a collection with the help of find() method −
> db.getDistinctDemo.find().pretty();
This will produce the following output −
{ "_id" : ObjectId("5cef69f9ef71edecf6a1f69d"), "Values" : [ 100, 200 ] } { "_id" : ObjectId("5cef6a07ef71edecf6a1f69e"), "Values" : [ 300, 100 ] }
Following is the query to get distinct levels of array field in MongoDB −
> db.getDistinctDemo.aggregate([ { "$group": { "_id": 0, "MyValues": { "$addToSet": "$Values" } } } ]);
This will produce the following output −
{ "_id" : 0, "MyValues" : [ [ 300, 100 ], [ 100, 200 ] ] }
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