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MongoDB aggregation group and remove duplicate array values?
Use MongoDB aggregate for this and within that, use $group. Let us create a collection with documents −
> db.demo649.insertOne(
... { "_id" : 101, "Names" : [ "John", "Bob", "Bob", "Robert" ], "CountryName" : "US" }
... );
{ "acknowledged" : true, "insertedId" : 101 }
>
> db.demo649.insertOne({ "_id" :102, "Names" : [ "John", "Robert" ], "CountryName" : "UK"});
{ "acknowledged" : true, "insertedId" : 102 }Display all documents from a collection with the help of find() method −
> db.demo649.find();
This will produce the following output −
{ "_id" : 101, "Names" : [ "John", "Bob", "Bob", "Robert" ], "CountryName" : "US" }
{ "_id" : 102, "Names" : [ "John", "Robert" ], "CountryName" : "UK" }Following is the query for aggregation group −
> db.demo649.aggregate(
... { $unwind : "$Names"},
... { $group : { _id : "$_id" , Names : { $addToSet : "$Names" } ,
... CountryName : { $first : "$CountryName" }}}
... )This will produce the following output −
{ "_id" : 102, "Names" : [ "Robert", "John" ], "CountryName" : "UK" }
{ "_id" : 101, "Names" : [ "Robert", "Bob", "John" ], "CountryName" : "US" }
Updated on: 12-May-2020
2K+ Views
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