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What kind of MongoDB query finds same value multiple times in an array?
To find same value multiple times, use $where in MongoDB. Let us create a collection with documents −
> db.demo188.insertOne(
... {
... "ListOfData":[
... {"Data": 100},
... {"Data": 200},
... {"Data": 100}
... ]
... }
...);
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3ad1c203d395bdc21346bd")
}
> db.demo188.insertOne(
... {
... "ListOfData":[
... {"Data": 100},
... {"Data": 200},
... {"Data": 300}
... }
...);
{
"acknowledged" : true,
"insertedId" : ObjectId("5e3ad1c203d395bdc21346be")
}Display all documents from a collection with the help of find() method −
> db.demo188.find();
This will produce the following output −
{ "_id" : ObjectId("5e3ad1c203d395bdc21346bd"), "ListOfData" : [ { "Data" : 100 }, { "Data" : 200 }, { "Data" : 100 } ] }
{ "_id" : ObjectId("5e3ad1c203d395bdc21346be"), "ListOfData" : [ { "Data" : 100 }, { "Data" : 200 }, { "Data" : 300 } ] }Following is the query to find same value multiple times in an array −
> db.demo188.find({
... "$where": function() {
... return this.ListOfData.filter(function(d) {
... return d.Data == 100;
... }).length > 1;
... }
...})This will produce the following output −
{ "_id" : ObjectId("5e3ad1c203d395bdc21346bd"), "ListOfData" : [ { "Data" : 100 }, { "Data" : 200 }, { "Data" : 100 } ] }
Updated on: 27-Mar-2020
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