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In MongoDB, what is the most efficient way to get the first and last document?
To get the first and last document in MongoDB, use aggregate() along with $first and $last respectively. Let us create a collection with documents −
> db.demo73.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e29c41b71bf0181ecc4226c") } . > db.demo73.insertOne({"Name":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e29c41e71bf0181ecc4226d") } > db.demo73.insertOne({"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e29c42271bf0181ecc4226e") }
Display all documents from a collection with the help of find() method −
> db.demo73.find();
This will produce the following output −
{ "_id" : ObjectId("5e29c41b71bf0181ecc4226c"), "Name" : "Chris" } { "_id" : ObjectId("5e29c41e71bf0181ecc4226d"), "Name" : "Bob" } { "_id" : ObjectId("5e29c42271bf0181ecc4226e"), "Name" : "David" }
Following is the way to get the first and last document−
> db.demo73.aggregate({ ... $group: { ... _id: null, ... first: { $first: "$$ROOT" }, ... last: { $last: "$$ROOT" } ... } ... } ... );
This will produce the following output −
{ "_id" : null, "first" : { "_id" : ObjectId("5e29c41b71bf0181ecc4226c"), "Name" : "Chris" }, "last" : { "_id" : ObjectId("5e29c42271bf0181ecc4226e"), "Name" : "David" } }
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