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Found 1359 Articles for MongoDB
503 Views
To auto increment in MongoDB to store a sequence of unique user id, let us create a collection which contains information about last sequence values of all documents.Let us first create a collection. The query to create a collection which is as follows −> db.createSequenceDemo.insertOne({_id:"SID", S_Value:0}); { "acknowledged" : true, "insertedId" : "SID" }Now, we will create a function that will generate an auto increment in MongoDB to store sequence. The query is as follows −> function nextSequence(s) { ... var sd = db.createSequenceDemo.findAndModify({ ... query:{_id: s }, ... update: {$inc:{S_Value:1}}, ... Read More
265 Views
Use the aggregate framework to find all duplicate documents in a MongoDB collection by a key field.To understand the concept, let us create a collection with the document. The query to create a collection with a document is as follows −> db.findDuplicateByKeyDemo.insertOne({"StudentId":1, "StudentName":"John"}); { "acknowledged" : true, "insertedId" : ObjectId("5c7f5b168d10a061296a3c3a") } > db.findDuplicateByKeyDemo.insertOne({"StudentId":2, "StudentName":"Carol"}); { "acknowledged" : true, "insertedId" : ObjectId("5c7f5b1f8d10a061296a3c3b") } > db.findDuplicateByKeyDemo.insertOne({"StudentId":3, "StudentName":"Carol"}); { "acknowledged" : true, "insertedId" : ObjectId("5c7f5b248d10a061296a3c3c") } > db.findDuplicateByKeyDemo.insertOne({"StudentId":4, "StudentName":"John"}); { "acknowledged" : true, "insertedId" : ObjectId("5c7f5b2d8d10a061296a3c3d") } > db.findDuplicateByKeyDemo.insertOne({"StudentId":5, "StudentName":"Sam"}); { "acknowledged" : true, ... Read More
341 Views
You need to use some code in order to convert a string to numerical values in MongoDB.Let us first create a collection with a document. The query to create a collection with a document is as follows:> db.convertStringToNumberDemo.insertOne({"EmployeeId":"101", "EmployeeName":"Larry"}); { "acknowledged" : true, "insertedId" : ObjectId("5c7f56528d10a061296a3c31") } > db.convertStringToNumberDemo.insertOne({"EmployeeId":"1120", "EmployeeName":"Mike"}); { "acknowledged" : true, "insertedId" : ObjectId("5c7f56648d10a061296a3c32") } > db.convertStringToNumberDemo.insertOne({"EmployeeId":"3210", "EmployeeName":"Sam"}); { "acknowledged" : true, "insertedId" : ObjectId("5c7f566e8d10a061296a3c33") }Display all documents from the collection with the help of find() method. The query is as follows −> db.convertStringToNumberDemo.find().pretty();The following is the output −{ "_id" ... Read More
253 Views
The $unwind operator in MongoDB is the same for each array, it returns the mapping document. Here is the demo of $unwind operator in MongoDB.To understand the concept, let us create a collection with the document. The query to create a collection with a document is as follows −> db.unwindOperatorDemo.insertOne({"StudentName":"Larry", "StudentAge":23, "StudentSubje ct":["C", "C++", "Java", "MongoDB"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c7ef5f3559dd2396bcfbfc8") }Display all documents from a collection with the help of find() method. The query is as follows −> db.unwindOperatorDemo.find().pretty();The following is the output −{ "_id" : ObjectId("5c7ef5f3559dd2396bcfbfc8"), "StudentName" : "Larry", "StudentAge" : ... Read More
759 Views
You can use $all operator to find by multiple array items. To understand the concept, let us create a collection with the document.The query to create a collection with a document is as follows −> db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"John", "StudentLastName":"Smith", "StudentCoreSubject":["Compiler", "Operating System", "Computer Networks"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c7ef07b559dd2396bcfbfc4") } > db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"Carol", "StudentLastName":"Taylor", "StudentCoreSubject":["MongoDB", "MySQL", "SQL Server"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c7ef09d559dd2396bcfbfc5") } > db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"Bob", "StudentLastName":"Taylor", "StudentCoreSubject":["MongoDB", "MySQL", "SQL Server"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c7ef0c7559dd2396bcfbfc6") } > db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"David", "StudentLastName":"Johnson", "StudentCoreSubject":["Compiler", "Operating System", "Computer Networks"]}); { ... Read More
93 Views
You can use $in operator to find with multiple array items. To understand the concept, let us create a collection with the document.The query to create a collection with a document is as follows −>db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"John", "StudentLastName":"Smith", "StudentCoreSubject":["Compiler", "Operating System", "Computer Networks"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c7ef07b559dd2396bcfbfc4") } >db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"Carol", "StudentLastName":"Taylor", "StudentCoreSubject":["MongoDB", "MySQL", "SQL Server"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c7ef09d559dd2396bcfbfc5") } >db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"Bob", "StudentLastName":"Taylor", "StudentCoreSubject":["MongoDB", "MySQL", "SQL Server"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c7ef0c7559dd2396bcfbfc6") } >db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"David", "StudentLastName":"Johnson", "StudentCoreSubject":["Compiler", "Operating System", "Computer Networks"]}); { "acknowledged" : true, ... Read More
2K+ Views
You can use update() function to insert records in MongoDB if it does not exist. To understand the concept, let us create a collection with the document. The query to create a collection with a document is as follows −> db.insertIfNotExistsDemo.insertOne({"StudentName":"Mike", "StudentAge":21}); { "acknowledged" : true, "insertedId" : ObjectId("5c7eec7b559dd2396bcfbfc2") } > db.insertIfNotExistsDemo.insertOne({"StudentName":"Sam", "StudentAge":22}); { "acknowledged" : true, "insertedId" : ObjectId("5c7eec97559dd2396bcfbfc3") }Display all documents from a collection with the help of find() method. The query is as follows −> db.insertIfNotExistsDemo.find().pretty(); The following is the output: { "_id" : ObjectId("5c7eec7b559dd2396bcfbfc2"), "StudentName" : "Mike", "StudentAge" : ... Read More
223 Views
The syntax is as follows to rename a field for all documents. Here, we have used $renameLdb.yourCollectionName.update({}, {$rename:{"yourOldFieldName":"yourNewFieldName"}}, false, true);To understand the concept, let us create a collection with the document. The query to create a collection with a document is as follows −> db.renameFieldDemo.insertOne({"StudentName":"John"}); { "acknowledged" : true, "insertedId" : ObjectId("5c7ee6c7559dd2396bcfbfbb") } > db.renameFieldDemo.insertOne({"StudentName":"Carol"}); { "acknowledged" : true, "insertedId" : ObjectId("5c7ee6cb559dd2396bcfbfbc") } > db.renameFieldDemo.insertOne({"StudentName":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5c7ee6cf559dd2396bcfbfbd") } > db.renameFieldDemo.insertOne({"StudentName":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5c7ee6d3559dd2396bcfbfbe") } > db.renameFieldDemo.insertOne({"StudentName":"Maxwell"}); { "acknowledged" : true, "insertedId" ... Read More
118 Views
You can use the aggregate framework to get a particular element from the MongoDB array. To understand the concept, let us create a collection with the document. The query to create a collection with the document is as follows −> db.getParticularElement.insertOne({"InstructorName":"Larry", "InstructorTechnicalSubject":["Java", "C", "C++", "MongoDB", "MySQL", "SQL Server"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c7ee027559dd2396bcfbfb1") }Display all documents from a collection with the help of find() method. The query is as follows −> db.getParticularElement.find().pretty();The following is the output −{ "_id" : ObjectId("5c7ee027559dd2396bcfbfb1"), "InstructorName" : "Larry", "InstructorTechnicalSubject" : [ "Java", ... Read More
685 Views
To get the storage size of a database in MongoDB, use the stats() method.At first, check the current database with the help of the following query −> db;The following is the output −testHere is the query to get the storage size of the database in MongoDB −> db.stats()The following is the output displaying the stats including the storage size −The following is the output −{ "db" : "test", "collections" : 114, "views" : 0, "objects" : 391, "avgObjSize" : 83.0076726342711, "dataSize" : 32456, "storageSize" : 3211264, "numExtents" : 0, "indexes" : 120, "indexSize" : 2494464, "fsUsedSize" : 126172377088, "fsTotalSize" : 199229435904, "ok" : 1 }