To get index of an array element, use $indexOfArray. Let us create a collection with documents −> db.demo65.insertOne({"ListOfValues":[10, 20, 30]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e28990ecfb11e5c34d89938") } > db.demo65.insertOne({"ListOfValues":[50, 60, 70, 100]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e28991ecfb11e5c34d89939") } > db.demo65.insertOne({"ListOfValues":[30, 40, 89, 91, 98]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e28992bcfb11e5c34d8993a") }Display all documents from a collection with the help of find() method −> db.demo65.find();This will produce the following output −{ "_id" : ObjectId("5e28990ecfb11e5c34d89938"), "ListOfValues" : [ 10, 20, 30 ] } { "_id" : ObjectId("5e28991ecfb11e5c34d89939"), "ListOfValues" : [ 50, 60, ... Read More

To calculate average of a particular field, use aggregate() along with $avg. Let us create a collection with documents −> db.demo214.insertOne({"Marks":56, "Name":"David"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3e319403d395bdc2134705") } > db.demo214.insertOne({"Marks":86, "Name":"Bob"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3e319c03d395bdc2134706") } > db.demo214.insertOne({"Marks":78, "Name":"Carol"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3e31a403d395bdc2134707") }Display all documents from a collection with the help of find() method −> db.demo214.find();This will produce the following output −{ "_id" : ObjectId("5e3e319403d395bdc2134705"), "Marks" : 56, "Name" : "David" } { "_id" : ObjectId("5e3e319c03d395bdc2134706"), "Marks" : 86, "Name" : "Bob" } { "_id" ... Read More

To merge, use aggregate() along with $PUSH. Let us create a collection with documents −> db.demo64.insertOne({"Subjects":["MySQL", "MongoDB", "Java"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e28762bcfb11e5c34d89936") } > db.demo64.insertOne({"Subjects":["Oracle", "Spring", "Python"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e28763fcfb11e5c34d89937") }Display all documents from a collection with the help of find() method −> db.demo64.find();This will produce the following output −{ "_id" : ObjectId("5e28762bcfb11e5c34d89936"), "Subjects" : [ "MySQL", "MongoDB", "Java" ] } { "_id" : ObjectId("5e28763fcfb11e5c34d89937"), "Subjects" : [ "Oracle", "Spring", "Python" ] }Following is the query to merge array of document in MongoDB −> db.demo64.aggregate([ ... { "$group": { ... Read More

You need to use $group to group documents with specified _id expression. Let us first create a collection with documents −> db.aggreagateDemo.insertOne({"Product_Id":1, "ProductPrice":50}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06d3c025ddae1f53b621d9") } > db.aggreagateDemo.insertOne({"Product_Id":2, "ProductPrice":100}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06d3c625ddae1f53b621da") } > db.aggreagateDemo.insertOne({"Product_Id":2, "ProductPrice":500}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06d3cb25ddae1f53b621db") } > db.aggreagateDemo.insertOne({"Product_Id":1, "ProductPrice":150}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06d3d125ddae1f53b621dc") }Following is the query to display all documents from a collection with the help of find() method −> db.aggreagateDemo.find().pretty();This will produce the following output −{    "_id" : ObjectId("5e06d3c025ddae1f53b621d9"), ... Read More

To check for existence of a record, use findOne() in MongoDB. Let us first create a collection with documents −> db.existsAlternateDemo.insertOne({"StudentName":"Chris"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06d23f9e4dae213890ac5c") } > db.existsAlternateDemo.insertOne({"StudentName":"Chris", "StudentAge":21}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06d2559e4dae213890ac5d") } >db.existsAlternateDemo.insertOne({"StudentName":"Chris", "StudentAge":22, "StudentCountryName":"US"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06d2689e4dae213890ac5e") }Following is the query to display all documents from a collection with the help of find() method −> db.existsAlternateDemo.find();This will produce the following output −{ "_id" : ObjectId("5e06d23f9e4dae213890ac5c"), "StudentName" : "Chris" } { "_id" : ObjectId("5e06d2559e4dae213890ac5d"), "StudentName" : "Chris", "StudentAge" : 21 } { ... Read More

To sum specific fields, use aggregate along with $sum. Let us first create a collection with documents −> db.getSumOfFieldsDemo.insertOne({"Customer_Id":101, "Price":50, "Status":"Active"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06cec29e4dae213890ac55") } > db.getSumOfFieldsDemo.insertOne({"Customer_Id":102, "Price":200, "Status":"Inactive"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06ced19e4dae213890ac56") } > db.getSumOfFieldsDemo.insertOne({"Customer_Id":101, "Price":3000, "Status":"Active"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06cedd9e4dae213890ac57") } > db.getSumOfFieldsDemo.insertOne({"Customer_Id":103, "Price":400, "Status":"Active"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e06cee79e4dae213890ac58") }Following is the query to display all documents from a collection with the help of find() method −> db.getSumOfFieldsDemo.find().pretty();This will produce the following output −{    "_id" : ... Read More

To insert records in MongoDB and avoid duplicates, use “unique:true”. Let us first create a collection with documents.Here, we are trying to add duplicate records −> db.insertWithoutDuplicateDemo.createIndex({"StudentFirstName":1}, { unique: true } ); {    "createdCollectionAutomatically" : true,    "numIndexesBefore" : 1,    "numIndexesAfter" : 2,    "ok" : 1 } > db.insertWithoutDuplicateDemo.insert({"StudentFirstName":"Chris"}, { upsert: true }); WriteResult({ "nInserted" : 1 }) > db.insertWithoutDuplicateDemo.insert({"StudentFirstName":"David"}, { upsert: true }); WriteResult({ "nInserted" : 1 }) > db.insertWithoutDuplicateDemo.insert({"StudentFirstName":"Chris"}, { upsert: true }); WriteResult({    "nInserted" : 0,    "writeError" : {       "code" : 11000,       "errmsg" : "E11000 duplicate ... Read More

To apply a condition, use $setIsSubset. Let us first create a collection with documents −> db.subsetDemo.insertOne({"StudentName":"Chris", "StudentFavouriteSubject":["Java", "Python"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e063e49150ee0e76c06a052") } > db.subsetDemo.insertOne({"StudentName":"Chris", "StudentFavouriteSubject":["Java", "Python", "MySQL"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e063e4f150ee0e76c06a053") }Following is the query to display all documents from a collection with the help of find() method −> db.subsetDemo.find().pretty();This will produce the following output −{    "_id" : ObjectId("5e063e49150ee0e76c06a052"),    "StudentName" : "Chris",    "StudentFavouriteSubject" : [       "Java",       "Python"    ] } {    "_id" : ObjectId("5e063e4f150ee0e76c06a053"),    "StudentName" : "Chris",   ... Read More

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