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How can I extract entire documents based on how they compare with their whole collection?
For this, use $$ROOT in MongoDB. Let us create a collection with documents −
> db.demo743.insertOne({id:1,"ShippingDate":"2020-01-21",value:50});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ead893a57bb72a10bcf0680")
}
> db.demo743.insertOne({id:2,"ShippingDate":"2020-05-10",value:30});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ead893c57bb72a10bcf0681")
}
> db.demo743.insertOne({id:3,"ShippingDate":"2020-05-10",value:60});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ead894657bb72a10bcf0682")
}
> db.demo743.insertOne({id:1,"ShippingDate":"2020-05-11",value:75});
{
"acknowledged" : true,
"insertedId" : ObjectId("5ead895657bb72a10bcf0683")
}Display all documents from a collection with the help of find() method −
> db.demo743.find();
This will produce the following output −
{ "_id" : ObjectId("5ead893a57bb72a10bcf0680"), "id" : 1, "ShippingDate" : "2020-01-21", "value" : 50 }
{ "_id" : ObjectId("5ead893c57bb72a10bcf0681"), "id" : 2, "ShippingDate" : "2020-05-10", "value" : 30 }
{ "_id" : ObjectId("5ead894657bb72a10bcf0682"), "id" : 3, "ShippingDate" : "2020-05-10", "value" : 60 }
{ "_id" : ObjectId("5ead895657bb72a10bcf0683"), "id" : 1, "ShippingDate" : "2020-05-11", "value" : 75 }Following is the query to extract entire documents based on how they compare with their whole collection −
> db.demo743.aggregate([
... {
... "$project":
... {
... "id": "$id",
... "ShippingDate": "$ShippingDate",
... "MyDoc": "$$ROOT"
... }
... },
... {
... "$sort":
... { "ShippingDate": -1
... }
... },
... {
... "$group":
... {
... "_id":{"id":"$id"},
... "Result":{"$first":"$MyDoc"}
... }
... },
... {
... $project:
... {
... "Result.ShippingDate":1, "Result.id":1, "Result.value":1, _id:0}
... }
... ])This will produce the following output −
{ "Result" : { "id" : 3, "ShippingDate" : "2020-05-10", "value" : 60 } }
{ "Result" : { "id" : 2, "ShippingDate" : "2020-05-10", "value" : 30 } }
{ "Result" : { "id" : 1, "ShippingDate" : "2020-05-11", "value" : 75 } }
Updated on: 30-Jun-2020
60 Views
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