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To aggregate nested documents in MongoDB, you can use $group. Let us first create a collection with documents −> db.aggregateDemo.insertOne( ... { ... "ProductInformation": [ ... { ... "Product1": [ ... { ... Amount: 50 ... }, ... { ... Amount: 90 ... ... Read More
To update, just save new ID and remove the old one using remove(). Let us first create a collection with documents −> db.updatingDemo.insertOne({"StudentName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5e04dae5150ee0e76c06a04b") } > db.updatingDemo.insertOne({"StudentName":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e04dae7150ee0e76c06a04c") }Following is the query to display all documents from a collection with the help of find() method −> db.updatingDemo.find();This will produce the following output −{ "_id" : ObjectId("5e04dae5150ee0e76c06a04b"), "StudentName" : "Robert" } { "_id" : ObjectId("5e04dae7150ee0e76c06a04c"), "StudentName" : "Bob" }Here is the query to update _id in MongoDB −> myDocument = db.updatingDemo.findOne({"StudentName":"Bob"}); { "_id" : ObjectId("5e04dae7150ee0e76c06a04c"), ... Read More
To add a column, you need to update the collection. The syntax is as follows −db.getCollection(yourCollectionName).update({}, {$set: {"yourColumnName": "yourValue"}}, false, true);To understand the above syntax, let us create a collection with documents −> db.addColumnDemo.insertOne({"StudentId":101, "StudentName":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e04d66af5e889d7a519950f") } > db.addColumnDemo.insertOne({"StudentId":102, "StudentName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5e04d673f5e889d7a5199510") } > db.addColumnDemo.insertOne({"StudentId":103, "StudentName":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e04d67bf5e889d7a5199511") }Following is the query to display all documents from a collection with the help of find() method −> db.addColumnDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e04d66af5e889d7a519950f"), ... Read More
To check for a specific value, use $in. Let us first create a collection with documents −> db.testInArray.insertOne({"ListOfNumbers":[10, 56, 78, 90, 32]}); { "acknowledged" : true, "insertedId" : ObjectId("5e04d42df5e889d7a519950d") } > db.testInArray.insertOne({"ListOfNumbers":[56, 78, 91, 100]}); { "acknowledged" : true, "insertedId" : ObjectId("5e04d588f5e889d7a519950e") }Following is the query to display all documents from a collection with the help of find() method −> db.testInArray.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e04d42df5e889d7a519950d"), "ListOfNumbers" : [ 10, 56, 78, 90, 32 ... Read More
For this, simply use find(). For a different format, use pretty(). Let us first create a collection with documents −> db.getSpecificData.insertOne( ... { ... "StudentName": "John", ... "Information": { ... "FatherName": "Chris", ... "Place": { ... "CountryName": "US", ... "ZipCode":"111344" ... }, ... "id": "1" ... } ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e039abdf5e889d7a5199509") } > db.getSpecificData.insertOne( ... { ... "StudentName": "Carol", ... "Information": ... Read More
To copy rows into another collection, use MongoDB. The syntax is as follows wherein “yourOldCollectionName” is the old collection, whereas where this collection will get copied is our new collection i.e. “yourNewCollectionName” −db.yourOldCollectionName.aggregate([{ $sample: { size: 333333 }}, {$out: "yourNewCollectionName"} ], {allowDiskUse: true});Let us first create a collection with documents −> db.sourceCollection.insertOne({"EmployeeName":"Robert", "EmployeeSalary":15000}); { "acknowledged" : true, "insertedId" : ObjectId("5e0397c1f5e889d7a5199506") } > db.sourceCollection.insertOne({"EmployeeName":"David", "EmployeeSalary":25000}); { "acknowledged" : true, "insertedId" : ObjectId("5e0397c3f5e889d7a5199507") } > db.sourceCollection.insertOne({"EmployeeName":"Mike", "EmployeeSalary":29000}); { "acknowledged" : true, "insertedId" : ObjectId("5e0397c4f5e889d7a5199508") }Following is the query to display all documents from a collection with ... Read More
In this case, use the concept of index on a particular field. Let us first create a collection with documents. Here, we have created index as well using createIndex() −> db.decreasetimeusingindex.createIndex({"StudentName":1}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.decreasetimeusingindex.insertOne({"StudentName":"John Smith", "StudentAge":21}); { "acknowledged" : true, "insertedId" : ObjectId("5e03960af5e889d7a51994ff") } > db.decreasetimeusingindex.insertOne({"StudentName":"John Doe", "StudentAge":24}); { "acknowledged" : true, "insertedId" : ObjectId("5e039611f5e889d7a5199500") } > db.decreasetimeusingindex.insertOne({"StudentName":"Adam Smith", "StudentAge":22}); { "acknowledged" : true, "insertedId" : ObjectId("5e03961df5e889d7a5199501") }Following is the query to display all documents from a ... Read More
Extract a particular element from a nested array with the help of dot(.) notation. Let us first create a collection with documents −> db.extractParticularElementDemo.insertOne( ... { ... "_id" : 101, ... "StudentName" : "John", ... "StudentInformation" : [ ... { ... "Age" : 21, ... "StudentPersonalInformation" : [ ... { ... "StudentNickName" : "Mike", ... ... Read More
Java 9 introduces the JShell tool for the Java Programming Language. This tool allows us to evaluate code snippets such as declarations, statements, and expressions. We will get the details about Java Version and Vendor, and also get the details about OS Version and Name by using the static method: getProperty() of System class.In the below code snippet, we can able to get the details of Java version, Java Vendor and OS version and OS name in JShell console.C:\Users\User>jshell | Welcome to JShell -- Version 9.0.4 | For an introduction type: /help intro jshell> System.out.println(System.getProperty("java.version")); 9.0.4 jshell> System.out.println(System.getProperty("java.vendor")); Oracle ... Read More
Use MongoDB $literal to set a string literal. Let us first create a collection with documents −>db.replacevaluedemo.insertOne({"StudentName":"Chris", "StudentFavouriteSubject":{"TeacherName":"Bob", "SubjectCode":"MySQL111"}}); { "acknowledged" : true, "insertedId" : ObjectId("5e0390a3f5e889d7a51994fd") } >db.replacevaluedemo.insertOne({"StudentName":"Mike", "StudentFavouriteSubject":{"TeacherName":"David", "SubjectCode":"3221Java"}}); { "acknowledged" : true, "insertedId" : ObjectId("5e0390b8f5e889d7a51994fe") }Following is the query to display all documents from a collection with the help of find() method −> db.replacevaluedemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e0390a3f5e889d7a51994fd"), "StudentName" : "Chris", "StudentFavouriteSubject" : { "TeacherName" : "Bob", "SubjectCode" : "MySQL111" } } { "_id" : ObjectId("5e0390b8f5e889d7a51994fe"), "StudentName" ... Read More