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To skip values in MongoDB, use skip() along with limit(). For 5 values, use limit(5). Let us create a collection with documents −> db.demo633.insertOne({"Value":10}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c0be76c954c74be91e6c1") } > db.demo633.insertOne({"Value":20}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c0bea6c954c74be91e6c2") } > db.demo633.insertOne({"Value":30}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c0bec6c954c74be91e6c3") } > db.demo633.insertOne({"Value":40}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c0bef6c954c74be91e6c4") } > db.demo633.insertOne({"Value":50}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c0bf16c954c74be91e6c5") } > db.demo633.insertOne({"Value":60}); { "acknowledged" : true, "insertedId" : ObjectId("5e9c0bf36c954c74be91e6c6") } > db.demo633.insertOne({"Value":70}); { "acknowledged" : ... Read More
To remove values from a matrix, use $pull in MongoDB. Let us create a collection with documents −> db.demo632.insertOne( ... { ... "arrayMatrix": [ ... [10, 20], ... [10, 20], ... [10, 20], ... [10, 20], ... [10, 20], ... [10, 20] ... ] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e9b27b46c954c74be91e6c0") }Display all documents from a collection with the help of find() ... Read More
Use $unwind twice for specific embedded document in MongoDB. Let us create a collection with documents −> db.demo631.insert( ... { ... id: "101", ... Info1: [ ... { ... CountryName : "US", ... Info2 : [ ... { ... Name:"Chris", ... Age:24 ... }, { ... Read More
To sort documents, use sort() along with find(). Let us create a collection with documents −> db.demo630.insertOne({"Value":10}); { "acknowledged" : true, "insertedId" : ObjectId("5e9b080e6c954c74be91e6ba") } > db.demo630.insertOne({"Value":200}); { "acknowledged" : true, "insertedId" : ObjectId("5e9b08116c954c74be91e6bb") } > db.demo630.insertOne({"Value":40}); { "acknowledged" : true, "insertedId" : ObjectId("5e9b08146c954c74be91e6bc") } > db.demo630.insertOne({"Value":60}); { "acknowledged" : true, "insertedId" : ObjectId("5e9b08176c954c74be91e6bd") }Display all documents from a collection with the help of find() method −> db.demo630.find();This will produce the following output −{ "_id" : ObjectId("5e9b080e6c954c74be91e6ba"), "Value" : 10 } { "_id" : ObjectId("5e9b08116c954c74be91e6bb"), "Value" : 200 } { "_id" : ... Read More
You can use $match. The $match filters the documents to pass only the documents that match the specified condition to the next pipeline stage. Let us create a collection with documents −> db.demo629.insertOne( ... { ... ... "Subject": [ ... "MySQL", ... "MongoDB" ... ], ... "details": [ ... { ... Name:"Chris", ... "Marks":78 ... }, ... { ... Read More
To query for values in list, use positional operator($) in MongoDB. Let us create a collection with documents −> db.demo628.insertOne({id:1, Name:["Chris", "David", "John"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e9ae7ea6c954c74be91e6b6") } > db.demo628.insertOne({id:1, Name:["Carol", "Sam"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e9ae7f26c954c74be91e6b7") } > db.demo628.insertOne({id:2, Name:["Mike", "Sam", "John"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e9ae8056c954c74be91e6b8") }Display all documents from a collection with the help of find() method −> db.demo628.find();This will produce the following output −{ "_id" : ObjectId("5e9ae7ea6c954c74be91e6b6"), "id" : 1, "Name" : [ "Chris", "David", "John" ] } { "_id" : ObjectId("5e9ae7f26c954c74be91e6b7"), "id" ... Read More
For this, use aggregate() along with $group. Let us create a collection with documents −> db.demo627.insertOne({id:101, "Name":"Chris", "Marks":54}); { "acknowledged" : true, "insertedId" : ObjectId("5e9acb306c954c74be91e6b2") } > db.demo627.insertOne({id:102, "Name":"Bob", "Marks":74}); { "acknowledged" : true, "insertedId" : ObjectId("5e9acb3c6c954c74be91e6b3") } > db.demo627.insertOne({id:101, "Name":"Chris", "Marks":87}); { "acknowledged" : true, "insertedId" : ObjectId("5e9acb426c954c74be91e6b4") } > db.demo627.insertOne({id:102, "Name":"Mike", "Marks":70}); { "acknowledged" : true, "insertedId" : ObjectId("5e9acb4b6c954c74be91e6b5") }Display all documents from a collection with the help of find() method −> db.demo627.find();This will produce the following output −{ "_id" : ObjectId("5e9acb306c954c74be91e6b2"), "id" : 101, "Name" : "Chris", "Marks" : ... Read More
For array interection in MongoDB, use the $setIntersection in aggregate(). Let us create a collection with documents −> db.demo625.insertOne( ... { ... Name: "John", ... Marks: [56, 98, 60] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e9ab8e16c954c74be91e6aa") } > db.demo625.insertOne( ... { ... Name: "John", ... Marks: [110, 56, 72] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e9ab8e26c954c74be91e6ab") } > db.demo625.insertOne( ... { ... Name: "Chris", ... ... Read More
Yes, you can use ensureIndex(). MongoDB provides complete support for indexes on any field in a collection of documents.Let us create a collection with documents −> db.demo622.ensureIndex({_id:1, Name:1, Age:1}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.demo622.insertOne({_id:101, Name:"Chris", Age:21}); { "acknowledged" : true, "insertedId" : 101 } > db.demo622.insertOne({_id:102, Name:"Chris", Age:22}); { "acknowledged" : true, "insertedId" : 102 } > db.demo622.insertOne({_id:103, Name:"Bob", Age:21}); { "acknowledged" : true, "insertedId" : 103 } > db.demo622.insertOne({_id:104, Name:"Chris", Age:22}); { "acknowledged" : true, "insertedId" : 104 } > db.demo622.insertOne({_id:104, Name:"Chris", Age:22}); 2020-04-18T12:21:18.085+0530 ... Read More
To aggregate second element from input element, use mapReduce(). Map-reduce is a data processing paradigm for condensing large volumes of data into useful aggregated results. Let us create a collection with documents −> db.demo621.insert({ _id: 101, Name1: "John", Name2: "John" }); WriteResult({ "nInserted" : 1 }) > db.demo621.insert({ _id: 102, Name1: "Bob", Name2: "John" }); WriteResult({ "nInserted" : 1 }) > db.demo621.insert({ _id: 103, Name1: "Chris", Name2: "John" }); WriteResult({ "nInserted" : 1 }) > db.demo621.insert({ _id: 104, Name1: "Sam", Name2: "John" }); WriteResult({ "nInserted" : 1 })Display all documents from a collection with the help of find() method −> ... Read More