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 More

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    } ]

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") } > ... Read More

To calculate average, use aggregate along with $avg. Let us first create a collection with documents −> db.calculateAverage.insertOne({'Value':[10, 20, 80]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e0383e3f5e889d7a51994dc") } > db.calculateAverage.insertOne({'Value':[12, 15, 16]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e0383edf5e889d7a51994dd") } > db.calculateAverage.insertOne({'Value':[30, 35, 40]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e0383f5f5e889d7a51994de") }Following is the query to display all documents from a collection with the help of find() method −> db.calculateAverage.find().pretty();This will produce the following output −{    "_id" : ObjectId("5e0383e3f5e889d7a51994dc"),    "Value" : [       10,       20,     ... Read More

To promote subfields to top level in projection, use $objectToArray and $arrayToObject. Let us first create a collection with documents:> db.promoteSubfieldsDemo.insertOne({'s':10, 'y':{'t':20, 'u':30, }}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e038004190a577c668b55d5") }Following is the query to display all documents from a collection with the help of find() method −> db.promoteSubfieldsDemo.find().pretty();This will produce the following output −{    "_id" : ObjectId("5e038004190a577c668b55d5"),    "s" : 10,    "y" : {       "t" : 20,       "u" : 30    } }Following is the query to promote subfields to top level in projection without listing all keys ... Read More

To delete specific record, use “$pull” and since we are updating the already created collection, use UPDATE().Let us create a collection with documents −> db.demo213.insertOne({ ...   "id": 101, ...   "details1": [ ...      { ...         "Name": "Chris", ...         "details2": [ ...            { ...               "StudentName": "David", ...               "Subject": "MongoDB" ...            }, ...            { ...               ... Read More

To find a MongoDB document through a word, use find() and set the word like −word/iLet us create a collection with documents −> db.demo212.insertOne({"details":[{"Name":"John Doe"}]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3e2c7603d395bdc21346ff") } > db.demo212.insertOne({"details":[{"Name":"Chris Brown"}]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3e2c8003d395bdc2134700") } > db.demo212.insertOne({"details":[{"Name":"Robert doe"}]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3e2c8a03d395bdc2134701") }Display all documents from a collection with the help of find() method −> db.demo212.find();This will produce the following output −{ "_id" : ObjectId("5e3e2c7603d395bdc21346ff"), "details" : [ { "Name" : "John Doe" } ] } { "_id" : ObjectId("5e3e2c8003d395bdc2134700"), "details" : ... Read More

To test the values, use $type. Let us create a collection with documents −> db.demo211.insertOne({id:101, "Name":"Chris"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3e298203d395bdc21346fa") } > db.demo211.insertOne({id:102, "Name":null}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3e2a5403d395bdc21346fb") }Display all documents from a collection with the help of find() method −> db.demo211.find();This will produce the following output −{ "_id" : ObjectId("5e3e298203d395bdc21346fa"), "id" : 101, "Name" : "Chris" } { "_id" : ObjectId("5e3e2a5403d395bdc21346fb"), "id" : 102, "Name" : null }Following is the query to test if two external values are equal in a MongoDB criteria object −> v1=200; 200 > v2=200; ... Read More

To get the count of a specific value in MongoDB, use aggregate(). Let us create a collection with documents −> db.demo210.insertOne( ...   { ...      details: [ ...         { ...            ClientName: "Robert" ...         }, ...         { ... ...            lientName: "John Doe" ...         }, ...         { ... ...            ClientName: "Robert" ...         }, ...         { ... ... ... Read More

To convert filed value to create datetime day of month, use MongoDB aggregate(). Let us create a collection with documents −> db.demo209.insertOne( ...   { ...      "_id" : "101", ...      "details" : [ ...         { ...            "dat" : 1528929908, ...            "Name" : "Chris" ...         }, ...         { ...            "dat" : 1529082069, ...            "Name":"Carol" ...         } ...      ], ... ... Read More