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

To convert numeric string to number, use parseInt() in MongoDB. Let us create a collection with documents −> db.demo208.insertOne( { "value":"50"} ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3d92d803d395bdc21346f6") } > db.demo208.insertOne( { "value":"2350"} ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3d92dd03d395bdc21346f7") }Display all documents from a collection with the help of find() method −> db.demo208.find();This will produce the following output −{ "_id" : ObjectId("5e3d92d803d395bdc21346f6"), "value" : "50" } { "_id" : ObjectId("5e3d92dd03d395bdc21346f7"), "value" : "2350" }Following is the query to convert numeric string to number −> db.demo208.find().forEach( function (doc) { ...   doc.value = parseInt(doc.value); ... Read More

Take the help of $addToSet in MongoDB to specify a return format. Let us create a collection with documents −> db.demo207.insertOne({"FavouriteTechnology":"Spring Boot"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3d8e7a03d395bdc21346f1") } > db.demo207.insertOne({"FavouriteTechnology":"MongoDB"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3d8e8f03d395bdc21346f2") } > db.demo207.insertOne({"FavouriteTechnology":"Groovy"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3d8ea603d395bdc21346f3") }Display all documents from a collection with the help of find() method −> db.demo207.find();This will produce the following output −{ "_id" : ObjectId("5e3d8e7a03d395bdc21346f1"), "FavouriteTechnology" : "Spring Boot" } { "_id" : ObjectId("5e3d8e8f03d395bdc21346f2"), "FavouriteTechnology" : "MongoDB" } { "_id" : ObjectId("5e3d8ea603d395bdc21346f3"), "FavouriteTechnology" : "Groovy" }Following is ... Read More

To determine if a specific value does not exist, use $ne in MongoDB. Let us create a collection with documents −> db.demo206.insertOne( ...   { ...      "ClientDetails": ...      [ ...         { ...            "Name":"Chris", ...            "Age":28, ...            "CountryName":"US" ...         } ...      ] ...   } ...); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3d8bd403d395bdc21346ee") } > db.demo206.insertOne( ...   { ...      "ClientDetails": ...      [ ...     ... Read More

To count records on the basis of matching criteria, use count(). Let us create a collection with documents −> db.demo205.insertOne( ...   { ... ...      "id": "101", ...      "Name": "", ...      "Age": "", ...      "isActive": false ...   } ...); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3d8a3003d395bdc21346eb") } > db.demo205.insertOne( ...   { ... ...      "id": "102", ...      "Name": "Chris", ...      "Age": "25", ...      "isActive": true ...   } ...); {    "acknowledged" : true,    "insertedId" : ObjectId("5e3d8a3003d395bdc21346ec") } > db.demo205.insertOne( ... Read More