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Found 1349 Articles for MongoDB
![Smita Kapse](https://www.tutorialspoint.com/assets/profiles/13597/profile/60_103706-1512718957.jpg)
250 Views
You can use the concept of map reduce to get the position in an array. Let us first create a collection with documents −> db.retrievePositionDemo.find(); { "_id" : ObjectId("5cd569ec7924bb85b3f4893f"), "Subjects" : [ "MySQL", "MongoDB", "Java" ] }Following is the query to display all documents from a collection with the help of find() method −> db.retrievePositionDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cd569ec7924bb85b3f4893f"), "Subjects" : [ "MySQL", "MongoDB", "Java" ] }Following is the query to retrieve the position in an array in MongoDB ... Read More
![Anvi Jain](https://www.tutorialspoint.com/assets/profiles/13591/profile/60_98631-1512716973.jpg)
524 Views
For MongoDB multidimensional array projection, you need to use aggregate framework. Let us first create a collection with documents. Here, we have multidimensional array for Student marks −> db.multiDimensionalArrayProjection.insertOne( ... { ... "StudentFirstName" : "Chris", ... "StudentMarks" : [ [98, 99], [56, 79] ] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5cc6b75a9cb58ca2b005e66c") }Following is the query to display all documents from a collection with the help of find() method −> db.multiDimensionalArrayProjection.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cc6b75a9cb58ca2b005e66c"), "StudentFirstName" : "Chris", "StudentMarks" ... Read More
![Nishtha Thakur](https://www.tutorialspoint.com/assets/profiles/13598/profile/60_104893-1512719058.jpg)
92 Views
You can use aggregate framework. Let us first create a collection with documents −> db.topCountArrayDemo.insertOne( ... {"StudentId":101 , "StudentSubject": ["C", "MongoDB"]} ... ); { "acknowledged" : true, "insertedId" : ObjectId("5cc6b3209cb58ca2b005e669") } > db.topCountArrayDemo.insertOne( ... {"StudentId":102 , "StudentSubject": ["C", "Java"]} ... ); { "acknowledged" : true, "insertedId" : ObjectId("5cc6b3219cb58ca2b005e66a") } > db.topCountArrayDemo.insertOne( ... {"StudentId":103 , "StudentSubject": ["C", "MongoDB"]} ... ); { "acknowledged" : true, "insertedId" : ObjectId("5cc6b3229cb58ca2b005e66b") }Following is the query to display all documents from a collection with the help of find() method −> db.topCountArrayDemo.find().pretty();This will produce the following output −{ ... Read More
![Smita Kapse](https://www.tutorialspoint.com/assets/profiles/13597/profile/60_103706-1512718957.jpg)
130 Views
To create a user in MongoDB v3, use the createUser() method. This allows you to create a user and while creating you need to add user, password, and roles as well. These roles assign permissions. The syntax is as follows −use admin db.createUser( { user: “yourUserName", pwd: "yourPassword", roles: [ { role: "yourPermission", db: "yourDatabase" } ] } );Let us implement the above syntax in order to create a user In MongoDB v3 −> use admin switched to db admin > db.createUser( ... { ... ... Read More
![Anvi Jain](https://www.tutorialspoint.com/assets/profiles/13591/profile/60_98631-1512716973.jpg)
360 Views
To select two fields and return a sorted array with distinct values, use aggregate framework along with $setUnion operator. Let us first create a collection with documents −> db.sortedArrayWithDistinctDemo.insertOne( ... { value1: 4, value2: 5} ... ); { "acknowledged" : true, "insertedId" : ObjectId("5cc690b99cb58ca2b005e666") } > db.sortedArrayWithDistinctDemo.insertOne( ... {value1: 5, value2: 6} ... ); { "acknowledged" : true, "insertedId" : ObjectId("5cc690b99cb58ca2b005e667") } > db.sortedArrayWithDistinctDemo.insertOne( ... {value1: 7, value2: 4} ... ); { "acknowledged" : true, "insertedId" : ObjectId("5cc690b99cb58ca2b005e668") }Following is the query to display all documents from a collection with the ... Read More
![Nishtha Thakur](https://www.tutorialspoint.com/assets/profiles/13598/profile/60_104893-1512719058.jpg)
281 Views
You can use $type operator to check whether a filed contains null value. Let us first create a collection with documents. We have also inserted a null in a field −> db.nullDemo.insertOne({"FirstName":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5cc68a1eac184d684e3fa270") } > db.nullDemo.insertOne({"FirstName":null}); { "acknowledged" : true, "insertedId" : ObjectId("5cc68a25ac184d684e3fa271") } > db.nullDemo.insertOne({"FirstName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5cc68a2cac184d684e3fa272") }Following is the query to display all documents from a collection with the help of find() method −> db.nullDemo.find().pretty();This will produce the following output. One of the field is null −{ "_id" : ObjectId("5cc68a1eac184d684e3fa270"), "FirstName" ... Read More
![Smita Kapse](https://www.tutorialspoint.com/assets/profiles/13597/profile/60_103706-1512718957.jpg)
465 Views
Let us first create a collection with a document −>db.useResultDemo.insertOne({"StudentFirstName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5cda70f5b50a6c6dd317adcd") }Display all documents from a collection with the help of find() method −> db.useResultDemo.find();Following is the output −{ "_id" : ObjectId("5cda70f5b50a6c6dd317adcd"), "StudentFirstName" : "Robert" }Here is the query to use result from MongoDB in shell script with var keyword −> var studentName=db.useResultDemo.findOne({},{_id:0}); > studentNameFollowing is the output −{ "StudentFirstName" : "Robert" }
![karthikeya Boyini](https://www.tutorialspoint.com/assets/profiles/13518/profile/60_31598-1537784993.jpg)
240 Views
Let us first create a collection with documents −> db.arrayContainOnlySpecificFieldDemo.insertOne( ... { ... "StudentName":"John", ... "StudentAge":21, ... "StudentTechnicalSubject":["C", "Java", "MongoDB"] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5cc4921dac184d684e3fa26a") } > db.arrayContainOnlySpecificFieldDemo.insertOne( { "StudentName":"Carol", "StudentAge":23, "StudentTechnicalSubject":["MongoDB"] } ); { "acknowledged" : true, "insertedId" : ObjectId("5cc49237ac184d684e3fa26b") }Display all documents from a collection with the help of find() method. The query is as follows −> db.arrayContainOnlySpecificFieldDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cc4921dac184d684e3fa26a"), "StudentName" : "John", "StudentAge" : 21, ... Read More
![Samual Sam](https://www.tutorialspoint.com/assets/profiles/13514/profile/60_83486-1512649303.jpg)
923 Views
To get attribute list from MongoDB object, you can use for loop to extract key and value for document. Let us create a collection with documents −>db.getAttributeListDemo.insertOne({"StudentId":101, "StudentName":"John", "StudentAdmissi onDate":new ISODate('2019-01-12'), "StudentSUbjects":["MongoDB", "Java", "MySQL"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cbdfcc9ac184d684e3fa269") }Display all documents from a collection with the help of find() method −> db.getAttributeListDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cbdfcc9ac184d684e3fa269"), "StudentId" : 101, "StudentName" : "John", "StudentAdmissionDate" : ISODate("2019-01-12T00:00:00Z"), "StudentSUbjects" : [ "MongoDB", "Java", "MySQL" ] }Following is the ... Read More
![karthikeya Boyini](https://www.tutorialspoint.com/assets/profiles/13518/profile/60_31598-1537784993.jpg)
87 Views
You can use findOne() for this. Following is the syntax −db.yourCollectionName.findOne({yourFieldName: 'yourValue'});Let us create a collection with documents −> db.checkExistingDemo.insertOne({"StudentName":"John"}); { "acknowledged" : true, "insertedId" : ObjectId("5cbdf90dac184d684e3fa265") } > db.checkExistingDemo.insertOne({"StudentName":"Carol"}); { "acknowledged" : true, "insertedId" : ObjectId("5cbdf912ac184d684e3fa266") } > db.checkExistingDemo.insertOne({"StudentName":"Sam"}); { "acknowledged" : true, "insertedId" : ObjectId("5cbdf916ac184d684e3fa267") } > db.checkExistingDemo.insertOne({"StudentName":"Mike"}); { "acknowledged" : true, "insertedId" : ObjectId("5cbdf91bac184d684e3fa268") }Display all documents from a collection with the help of find() method −> db.checkExistingDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cbdf90dac184d684e3fa265"), "StudentName" : "John" } { "_id" : ObjectId("5cbdf912ac184d684e3fa266"), "StudentName" : "Carol" } ... Read More