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Found 1349 Articles for MongoDB
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
6K+ Views
To select specific columns, you can ignore the rest of them i.e. to hide those columns, set them to 0. Let us first create a collection with documents −> db.demo415.insertOne({"ClientName":"Robert", "ClientCountryName":"US"}); { "acknowledged" : true, "insertedId" : ObjectId("5e72329db912067e57771adc") } > db.demo415.insertOne({"ClientName":"David", "ClientCountryName":"UK"}); { "acknowledged" : true, "insertedId" : ObjectId("5e7232acb912067e57771add") } > db.demo415.insertOne({"ClientName":"Bob", "ClientCountryName":"AUS"}); { "acknowledged" : true, "insertedId" : ObjectId("5e7232b4b912067e57771ade") }Display all documents from a collection with the help of find() method −> db.demo415.find();This will produce the following output −{ "_id" : ObjectId("5e72329db912067e57771adc"), "ClientName" : "Robert", "ClientCountryName" : "US" } { "_id" : ObjectId("5e7232acb912067e57771add"), ... Read More
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
696 Views
To find by _id on an array of objects, use aggregation and avoid using find(). Let us first create a collection with documents −> db.demo414.insertOne( ... { ... "_id": "110", ... "details":[ ... { ... "StudentName":"John", ... "StudentMarks":56 ... }, ... { ... "StudentName":"Robert", ... "StudentMarks":98 ... } ... ] ... } ... ); { "acknowledged" : true, "insertedId" : "110" }Display all documents from a collection with the help of find() method −> db.demo414.find();This will produce the following output −{ "_id" : "110", "details" : [ { "StudentName" : "John", "StudentMarks" : 56 }, { "StudentName" : "Robert", "StudentMarks" : 98 } ] }Following is the query to find by _id on an array of objects −> db.demo414.aggregate([{$unwind: "$details"}, {$match:{"details.StudentMarks" :56}}] )This will produce the following output −{ "_id" : "110", "details" : { "StudentName" : "John", "StudentMarks" : 56 } }
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
748 Views
Achieve this with aggregation pipeline. Let us first create a collection with documents −> db.demo413.insertOne( ... { ... "_id": "101", ... "details": { ... "Info1": { ... Name:"Chris", ... Age:21 ... }, ... "Info2": { ... Name:"David", ... Age:23 ... } ... } ... } ... ); { "acknowledged" : true, "insertedId" : "101" }Display all documents from a collection with the help of find() method −> db.demo413.find();This will produce the following output −{ "_id" : "101", "details" : { "Info1" : { "Name" : "Chris", "Age" : 21 }, "Info2" : { "Name" : "David", "Age" : 23 } } }Following is the query to exclude nested fields −> db.demo413.aggregate([ ... { $project: { "details" : { $objectToArray: "$details" } } }, ... { $project: { "details.v.Age" : 0} }, ... { $project: { "details" : { $arrayToObject: "$details"} } } ... ]);This will produce the following output −{ "_id" : "101", "details" : { "Info1" : { "Name" : "Chris" }, "Info2" : { "Name" : "David" } } }
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
204 Views
Let us create a collection with documents −> db.demo411.aggregate( ... [ ... {$project : { ... _id : 0, ... Information : {$map : {input : "$Information", as : "out", in : ["$$out.Name1", "$$out.Name2"]}} ... } ... } ... ] ... ) { "Information" : [ [ "Chris", "David" ], [ "John", "John" ] ] } > db.demo412.insertOne( ... { ... "Information1" : [ ... { ... ... Read More
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
810 Views
Let us create a collection with documents −> db.demo411.insertOne( ... { ... "Information" : [ ... { ... "Name1" : "Chris", ... "Name2" : "David" ... }, ... { ... "Name1" : "John", ... "Name2" : "John" ... } ... ] ... } ... ); { "acknowledged" : true, "insertedId" ... Read More
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
334 Views
To remove elements, use $pull and for such conditions, use $ne. The $ne in MongoDB is used to select the documents where the value of the field is not equal to the specified value.Let us create a collection with documents −> db.demo410.insertOne( ... { ... details: [{isMarried:false}, {isMarried:true}, {isMarried:false}, {isMarried:"Chris"}] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e70efc515dc524f70227681") }Display all documents from a collection with the help of find() method −> db.demo410.find();This will produce the following output −{ "_id" : ObjectId("5e70efc515dc524f70227681"), "details" : [ { "isMarried" : false }, { ... Read More
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
148 Views
To find documents with a specific string, use find() and in that search for a string with regex. Let us create a collection with documents −> db.demo409.insertOne({"Name":"John Doe"}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e4e515dc524f7022767c") } > db.demo409.insertOne({"Name":"Chris Brown"}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e4ec15dc524f7022767d") } > db.demo409.insertOne({"Name":"Robert Doe"}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e4f415dc524f7022767e") } > db.demo409.insertOne({"Name":"David Brown"}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e4fe15dc524f7022767f") }Display all documents from a collection with the help of find() method −> db.demo409.find();This will produce the following output −{ "_id" : ObjectId("5e70e4e515dc524f7022767c"), "Name" ... Read More
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
445 Views
To get a query plan in MongoDB, use explain(). The $explain operator gives information on the query plan.Let us create a collection with documents −> db.demo408.insertOne({"Value":50}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e3a115dc524f70227678") } > db.demo408.insertOne({"Value":20}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e3a715dc524f70227679") } > db.demo408.insertOne({"Value":45}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e3ac15dc524f7022767a") } > db.demo408.insertOne({"Value":35}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e3af15dc524f7022767b") } > db.demo408.createIndex({Value:1}); { "createdCollectionAutomatically" : false, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 }Display all documents from a collection with the help ... Read More
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
200 Views
To create a new user in MongoDB, use createUser(). Following is the query −> db.createUser( ... { ... user: "John", ... pwd: "123456", ... roles: [ { role: "readWrite", db: "test" } ], ... mechanisms: [ "SCRAM-SHA-256" ] ... } ... )This will produce the following output −Successfully added user: { "user" : "John", "roles" : [ { "role" : "readWrite", "db" : "test" } ], "mechanisms" : [ "SCRAM-SHA-256" ] }Following is the query to show all users −> db.getUsers();This will produce the following output −[ { "_id" : "test.John", "user" : "John", "db" : "test", "roles" : [ { "role" : "readWrite", "db" : "test" } ], "mechanisms" : [ "SCRAM-SHA-256" ] } ]
![AmitDiwan](https://www.tutorialspoint.com/assets/profiles/123055/profile/60_187394-1565938756.jpg)
97 Views
For this, use $setIsSubset in MongoDB. Let us create a collection with documents −> db.demo407.insertOne( ... { ... Name:"Chris", ... "details" : [ ... { ... id:100 ... }, ... { ... id:110 ... }, ... { ... id:130 ... } ... ] ... } ... ); ... Read More