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Found 6702 Articles for Database
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
45 Views
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
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
53 Views
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
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
517 Views
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
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
2K+ Views
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
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
56 Views
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
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
1K+ Views
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
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
86 Views
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
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
577 Views
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
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
310 Views
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
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
130 Views
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