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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 ] ] }
Updated on: 30-Jul-2019
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