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How to query on top N rows in MongoDB?
To query on top N rows in MongoDB, you can use aggregate framework. Let us create a collection with documents
> db.topNRowsDemo.insertOne({"StudentName":"Larry","Score":78});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ca26eee6304881c5ce84b91")
}
> db.topNRowsDemo.insertOne({"StudentName":"Chris","Score":45});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ca26ef66304881c5ce84b92")
}
> db.topNRowsDemo.insertOne({"StudentName":"Mike","Score":65});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ca26efe6304881c5ce84b93")
}
> db.topNRowsDemo.insertOne({"StudentName":"Adam","Score":55});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ca26f066304881c5ce84b94")
}
> db.topNRowsDemo.insertOne({"StudentName":"John","Score":86});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ca26f0f6304881c5ce84b95")
}Following is the query to display all documents from a collection with the help of find() method
> db.topNRowsDemo.find().pretty();
This will produce the following output
{
"_id" : ObjectId("5ca26eee6304881c5ce84b91"),
"StudentName" : "Larry",
"Score" : 78
}
{
"_id" : ObjectId("5ca26ef66304881c5ce84b92"),
"StudentName" : "Chris",
"Score" : 45
}
{
"_id" : ObjectId("5ca26efe6304881c5ce84b93"),
"StudentName" : "Mike",
"Score" : 65
}
{
"_id" : ObjectId("5ca26f066304881c5ce84b94"),
"StudentName" : "Adam",
"Score" : 55
}
{
"_id" : ObjectId("5ca26f0f6304881c5ce84b95"),
"StudentName" : "John",
"Score" : 86
}Here is how you can query on top N rows in MongoDB
> db.topNRowsDemo.aggregate([
... {$sort: {StudentName: 1}},
... {$limit: 5},
... {$match: {Score: {$gt: 65}}}
... ]).pretty();This will produce the following output
{
"_id" : ObjectId("5ca26f0f6304881c5ce84b95"),
"StudentName" : "John",
"Score" : 86
}
{
"_id" : ObjectId("5ca26eee6304881c5ce84b91"),
"StudentName" : "Larry",
"Score" : 78
}
Updated on: 30-Jul-2019
3K+ Views
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