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Articles on Trending Technologies
Technical articles with clear explanations and examples
Getting MongoDB results from the previous month\\n
At first, get the current month and subtract by 1 to fetch previous month records. Let us first create a collection with documents −> db.findOneMonthAgoData.insertOne({"CustomerName":"Chris", "PurchaseDate":new ISODate("2019-12-26")}); { "acknowledged" : true, "insertedId" : ObjectId("5e04e16c150ee0e76c06a04f") } > db.findOneMonthAgoData.insertOne({"CustomerName":"David", "PurchaseDate":new ISODate("2019-11-26")}); { "acknowledged" : true, "insertedId" : ObjectId("5e04e178150ee0e76c06a050") } > db.findOneMonthAgoData.insertOne({"CustomerName":"Bob", "PurchaseDate":new ISODate("2020-11-26")}); { "acknowledged" : true, "insertedId" : ObjectId("5e04e186150ee0e76c06a051") }Following is the query to display all documents from a collection with the help of find() method −> db.findOneMonthAgoData.find();This will produce the following output −{ "_id" : ObjectId("5e04e16c150ee0e76c06a04f"), "CustomerName" : "Chris", "PurchaseDate" : ISODate("2019-12-26T00:00:00Z") } { ...
Read MoreHow can I aggregate nested documents in MongoDB?\\n
To aggregate nested documents in MongoDB, you can use $group. Let us first create a collection with documents −> db.aggregateDemo.insertOne( ... { ... "ProductInformation": [ ... { ... "Product1": [ ... { ... Amount: 50 ... }, ... { ... Amount: 90 ... ...
Read MoreHow to add a column in MongoDB collection?
To add a column, you need to update the collection. The syntax is as follows −db.getCollection(yourCollectionName).update({}, {$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 MoreHow to get specific data in different formats with MongoDB?
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 MoreMongoDB - How to copy rows into a newly created collection?
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 MoreHow to get Java and OS version, vendor details in JShell in Java 9?
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 MoreReplace value with a string literal during MongoDB aggregation operation
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 MoreHow to count and sum a field between 2 dates in MongoDB?
Use aggregation $gte and $lte along with $sum to count and sum a field between 2 dates. Let us first create a collection with documents −> db.countandsumdemo.insertOne({"Value":10, "created_at":ISODate('2019-10-11')}); { "acknowledged" : true, "insertedId" : ObjectId("5e038e6df5e889d7a51994fa") } > db.countandsumdemo.insertOne({"Value":50, "created_at":ISODate('2019-01-31')}); { "acknowledged" : true, "insertedId" : ObjectId("5e038e77f5e889d7a51994fb") } > db.countandsumdemo.insertOne({"Value":100, "created_at":ISODate('2019-06-31')}); { "acknowledged" : true, "insertedId" : ObjectId("5e038e8af5e889d7a51994fc") }Following is the query to display all documents from a collection with the help of find() method −> db.countandsumdemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e038e6df5e889d7a51994fa"), "Value" : 10, "created_at" : ISODate("2019-10-11T00:00:00Z") ...
Read MoreBuild index in the background with MongoDB
To create index in the background, use createIndex() method and set “background: true” as in the below syntax −db.yourCollectionName.createIndex({"yourFieldName1":1,"yourFieldName2":1},{background: true} );Let us implement the above syntax in order to create index and set background −> db.indexCreationDemo.createIndex({"StudentName":1,"StudentAge":1},{background: true} ); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 }Let us display the indexes −> db.indexCreationDemo.getIndexes();This will produce the following output −[ { "v" : 2, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "web.indexCreationDemo" }, { "v" : 2, "key" : { "StudentName" : 1, "StudentAge" : 1 }, "name" : "StudentName_1_StudentAge_1", "ns" : "web.indexCreationDemo", "background" : true } ]
Read MoreFix: MongoDB Robomongo: db.data.find(…).collation is not a function?
The collation introduced in version MongoDB 3.4. Maybe, you implemented collation in a previous version.For our example, we are using MongoDB version 4.0.5. Following is the query to check the current version on system −> db.version()This will produce the following output −4.0.5Let us first create a collection with documents −> db.collationExample.createIndex({Value: 1}, {collation: {locale: "en", strength: 1}}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.collationExample.insertOne({'Value':'x'}); { "acknowledged" : true, "insertedId" : ObjectId("5e038a3cf5e889d7a51994f5") } > db.collationExample.insertOne({'Value':'X'}); { "acknowledged" : true, "insertedId" : ObjectId("5e038a48f5e889d7a51994f6") } > ...
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