Database Articles - Page 195 of 671

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 More

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

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