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Create an index and then use explain(). Let us create a collection with documents −> db.demo278.ensureIndex({"Subjects":1}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.demo278.insertOne({"Subjects":["MySQL", "MongoDB", "Java"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e49096edd099650a5401a55") } > db.demo278.insertOne({"Subjects":["C", "C++"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e490978dd099650a5401a56") } > db.demo278.insertOne({"Subjects":["Spring", "Hibernate"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e490984dd099650a5401a57") }Display all documents from a collection with the help of find() method −> db.demo278.find();This will produce the following output −{ "_id" : ObjectId("5e49096edd099650a5401a55"), "Subjects" : [ "MySQL", ... Read More
Let us first create a collection with documents −> db.demo277.insertOne({"details":[{"FirstName":"John"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e48fb21dd099650a5401a52") } > db.demo277.insertOne({"details":[{"FirstName":"David"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e48fb27dd099650a5401a53") } > db.demo277.insertOne({"details":[{"FirstName":"Chris"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e48fb2bdd099650a5401a54") }Display all documents from a collection with the help of find() method −> db.demo277.find();This will produce the following output −{ "_id" : ObjectId("5e48fb21dd099650a5401a52"), "details" : [ { "FirstName" : "John" } ] } { "_id" : ObjectId("5e48fb27dd099650a5401a53"), "details" : [ { "FirstName" : "David" } ] } { "_id" : ObjectId("5e48fb2bdd099650a5401a54"), "details" : [ { "FirstName" : ... Read More
To split a document by its subdocuments, use $unwind in MongoDB. Let us create a collection with documents −> db.demo276.insertOne({"Name":"Chris", "Subjects":["MySQL", "MongoDB"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e48f953dd099650a5401a51") }Display all documents from a collection with the help of find() method −> db.demo276.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e48f953dd099650a5401a51"), "Name" : "Chris", "Subjects" : [ "MySQL", "MongoDB" ] }Following is the query to split a document by its subdocuments −> db.demo276.aggregate( [ { $unwind : "$Subjects" } ] )This will produce the following output −{ ... Read More
To skip records in MongoDB, use skip(). With that, to display only a specific number of records, use limit().Let us create a collection with documents −> db.demo275.insertOne({"Number":10}); { "acknowledged" : true, "insertedId" : ObjectId("5e48eac4dd099650a5401a43") } > db.demo275.insertOne({"Number":12}); { "acknowledged" : true, "insertedId" : ObjectId("5e48eac7dd099650a5401a44") } > db.demo275.insertOne({"Number":6}); { "acknowledged" : true, "insertedId" : ObjectId("5e48eac9dd099650a5401a45") } > db.demo275.insertOne({"Number":1}); { "acknowledged" : true, "insertedId" : ObjectId("5e48eacadd099650a5401a46") } > db.demo275.insertOne({"Number":5}); { "acknowledged" : true, "insertedId" : ObjectId("5e48eacddd099650a5401a47") } > db.demo275.insertOne({"Number":24}); { "acknowledged" : true, "insertedId" : ObjectId("5e48ead0dd099650a5401a48") } > db.demo275.insertOne({"Number":8}); { ... Read More
Yes, you can achieve this by indexing like “properties.k” for key and “properties.v” for value. The same is used to be implemented in ensureIndex().Let us first see an example and create a collection with documents −> db.demo274.insertOne({"details":[{StudentFirstName:"Chris", StudentLastName:"Brown"}, ... {StudentFirstName:"David", StudentLastName:"Miller"}, ... {StudentFirstName:"John", StudentLastName:"Smith"}, ... {StudentFirstName:"John", StudentLastName:"Doe"} ...] ...} ...); { "acknowledged" : true, "insertedId" : ObjectId("5e48de35dd099650a5401a42") }Display all documents from a collection with the help of find() method −> db.demo274.find().pretty();OutputThis will produce the following output −{ "_id" : ObjectId("5e48de35dd099650a5401a42"), "details" : [ { "StudentFirstName" : ... Read More
To insert LONG numbers, use NumberLong(). It is used to handle 64-bit integers. Let us create a collection with documents −> db.demo273.insert({ ... Name:"Robert", ... id: NumberLong("100000000000001"), ... isActive:true ...}) WriteResult({ "nInserted" : 1 }) > db.demo273.insert({ ... Name:"David", ... id: NumberLong("98888888888888888"), ... isActive:false ...}) WriteResult({ "nInserted" : 1 }) > db.demo273.insert({ ... Name:"Mike", ... id: NumberLong("999999999999"), ... isActive:true ...}) WriteResult({ "nInserted" : 1 })Display all documents from a collection with the help of find() method −> db.demo273.find();OutputThis will produce the following output −{ "_id" : ObjectId("5e4824df1627c0c63e7dbac3"), "Name" : "Robert", "id" ... Read More
For this, you can use aggregate() in MongoDB. Let us create a collection with documents −> db.demo149.insertOne({"Status":40}); { "acknowledged" : true, "insertedId" : ObjectId("5e350386fdf09dd6d08539c4") } > db.demo149.insertOne({"Status":40}); { "acknowledged" : true, "insertedId" : ObjectId("5e350388fdf09dd6d08539c5") } > db.demo149.insertOne({"Status":50}); { "acknowledged" : true, "insertedId" : ObjectId("5e35038afdf09dd6d08539c6") }Display all documents from a collection with the help of find() method −> db.demo149.find();This will produce the following output −{ "_id" : ObjectId("5e350386fdf09dd6d08539c4"), "Status" : 40 } { "_id" : ObjectId("5e350388fdf09dd6d08539c5"), "Status" : 40 } { "_id" : ObjectId("5e35038afdf09dd6d08539c6"), "Status" : 50 }Here is the query to MongoDB group by ... Read More
To find records that does not match a condition, use $ne. Let us create a collection with documents −> db.demo148.insertOne({"Message":"Hello"}); { "acknowledged" : true, "insertedId" : ObjectId("5e32fb37fdf09dd6d08539c0") } > db.demo148.insertOne({"Message":"Good"}); { "acknowledged" : true, "insertedId" : ObjectId("5e32fb3efdf09dd6d08539c1") } > db.demo148.insertOne({"Message":"Bye"}); { "acknowledged" : true, "insertedId" : ObjectId("5e32fb42fdf09dd6d08539c2") }Display all documents from a collection with the help of find() method −> db.demo148.find();This will produce the following output −{ "_id" : ObjectId("5e32fb37fdf09dd6d08539c0"), "Message" : "Hello" } { "_id" : ObjectId("5e32fb3efdf09dd6d08539c1"), "Message" : "Good" } { "_id" : ObjectId("5e32fb42fdf09dd6d08539c2"), "Message" : "Bye" }Following is the query to ... Read More
To compare fields from an array, use $gt and $lt. Let us create a collection with documents −> db.demo147.insertOne({"Details":[{"Score":45}, {"Score":46}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e32fa21fdf09dd6d08539be") } > db.demo147.insertOne({"Details":[{"Score":65}, {"Score":86}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e32fa40fdf09dd6d08539bf") }Display all documents from a collection with the help of find() method −> db.demo147.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e32fa21fdf09dd6d08539be"), "Details" : [ { "Score" : 45 }, { "Score" : 46 } ... Read More
To remove an array element, simply use $pull along with update(). Let us create a collection with documents −> db.demo146.insertOne({"ListOfEmployeeNames":["Chris", "David", "Bob", "Mike"]}); { "acknowledged" : true, "insertedId" : ObjectId("5e32f54ffdf09dd6d08539bd") }Display all documents from a collection with the help of find() method −> db.demo146.find();This will produce the following output −{ "_id" : ObjectId("5e32f54ffdf09dd6d08539bd"), "ListOfEmployeeNames" : [ "Chris", "David", "Bob", "Mike" ] }Following is the query to remove an array element from MongoDB −> db.demo146.update({}, { "$pull": { "ListOfEmployeeNames": "Bob" } }); WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })Display all documents from a collection with ... Read More