For this, use $avg along with $group and aggregate(). Let us create a collection with documents −> db.demo598.insertOne( ...    { ...       Information:'Student', ...       id:100, ...       details:[ ...          {Name:'Chris', Marks:75}, ...          {Name:'Bob', Marks:55} ...       ] ...    } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e947fccf5f1e70e134e2694") } > db.demo598.insertOne( ...    { ...       Information:'Student', ...       id:101, ...       details:[ ...          {Name:'Chris', Marks:75}, ...     ... Read More

To find which document contains a specific string, use $regex along with find(). Let us create a collection with documents −> db.demo597.insertOne({"Name":"John Doe"});{    "acknowledged" : true, "insertedId" : ObjectId("5e947ae3f5f1e70e134e2690") } > db.demo597.insertOne({"Name":"John Smith"});{    "acknowledged" : true, "insertedId" : ObjectId("5e947ae8f5f1e70e134e2691") } > db.demo597.insertOne({"Name":"Chris Brown"});{    "acknowledged" : true, "insertedId" : ObjectId("5e947aeff5f1e70e134e2692") } > db.demo597.insertOne({"Name":"Adam Smith"});{    "acknowledged" : true, "insertedId" : ObjectId("5e947afff5f1e70e134e2693") }Display all documents from a collection with the help of find() method −> db.demo597.find();This will produce the following output −{ "_id" : ObjectId("5e947ae3f5f1e70e134e2690"), "Name" : "John Doe" } { "_id" : ObjectId("5e947ae8f5f1e70e134e2691"), "Name" : "John Smith" } ... Read More

Use findOne() in MongoDB for this. The findOne() returns one document that satisfies the specified query criteria on the collection.Let us create a collection with documents −> db.demo596.insertOne({_id:1, "FirstName":"John", "LastName":"Smith"}); { "acknowledged" : true, "insertedId" : 1 } > db.demo596.insertOne({_id:2, "FirstName":"John", "LastName":"Doe"}); { "acknowledged" : true, "insertedId" : 2 } > db.demo596.insertOne({_id:3, "FirstName":"Chris", "LastName":"Brown"}); { "acknowledged" : true, "insertedId" : 3 } > db.demo596.insertOne({_id:4, "FirstName":"David", "LastName":"Miller"}); { "acknowledged" : true, "insertedId" : 4 }Display all documents from a collection with the help of find() method −> db.demo596.find();This will produce the following output −{ "_id" : 1, "FirstName" : "John", "LastName" ... Read More

Let us create a collection with documents −> db.demo595.insertOne( { "Information": [    { "_id": new ObjectId(), Name:"Chris" },    { _id:new ObjectId(), Name:"Robert" } ] } ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e93369cfd2d90c177b5bce4") }Display all documents from a collection with the help of find() method −> db.demo595.find().pretty();This will produce the following output −{    "_id" : ObjectId("5e93369cfd2d90c177b5bce4"),    "Information" : [       {          "_id" : ObjectId("5e93369cfd2d90c177b5bce2"),          "Name" : "Chris"       },       {          "_id" : ObjectId("5e93369cfd2d90c177b5bce3"),     ... Read More

For this, use $slice. Let us create a collection with documents −> db.demo594.insertOne( ...    { ...       id:1, ...       details:[ ...          {Name:"Chris", Age:21}, ...          {Name:"Bob", Age:20}, ...          {Name:"David", Age:23}, ...          {Name:"Sam", Age:22} ...       ] ...    } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e933459fd2d90c177b5bcdd") }Display all documents from a collection with the help of find() method −> db.demo594.find();This will produce the following output −{ "_id" : ObjectId("5e933459fd2d90c177b5bcdd"), "id" : 1, "details" ... Read More

To fetch specific multiple documents in MongoDB, use $in. Let us create a collection with documents −> db.demo593.insertOne({id:1, "Name":"Chris"});{    "acknowledged" : true, "insertedId" : ObjectId("5e93177dfd2d90c177b5bcd9") } > db.demo593.insertOne({id:2, "Name":"John"});{    "acknowledged" : true, "insertedId" : ObjectId("5e931785fd2d90c177b5bcda") } > db.demo593.insertOne({id:3, "Name":"Bob"});{    "acknowledged" : true, "insertedId" : ObjectId("5e93178cfd2d90c177b5bcdb") } > db.demo593.insertOne({id:4, "Name":"Sam"});{    "acknowledged" : true, "insertedId" : ObjectId("5e931792fd2d90c177b5bcdc") }Display all documents from a collection with the help of find() method −> db.demo593.find();This will produce the following output −{ "_id" : ObjectId("5e93177dfd2d90c177b5bcd9"), "id" : 1, "Name" : "Chris" } { "_id" : ObjectId("5e931785fd2d90c177b5bcda"), "id" : 2, "Name" : "John" } ... Read More

To match documents that contain an array field, use the $elemMatch operator. Let us create a collection with documents −> db.demo592.insertOne( ...    { ...       "id":101, ...       "details" : [ ...          { "Name" : "Chris", "Value" : "200"}, ...          {"Name" : "David", "Value" : "800"} ...       ] ...    } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e930d8ffd2d90c177b5bcd6") } > db.demo592.insertOne( ... { ...    id:102, ...    "details" : [ ...       { "Name" : "Chris", "Value" ... Read More

To fetch a value from the nested document, use dot notation. Let us create a collection with documents −> db.demo591.insert([ ...    { "Name": "John", "Age": 23 }, ...    {"Name": "Carol", "Age": 26}, ...    { "Name": "Robert", "Age": 29, ...    details:[ ...       { ...          Email:"Robert@gmail.com", CountryName:"US"}, {"Post":35} ...       ]} ... ]); BulkWriteResult({    "writeErrors" : [ ],    "writeConcernErrors" : [ ],    "nInserted" : 3,    "nUpserted" : 0,    "nMatched" : 0,    "nModified" : 0,    "nRemoved" : 0,    "upserted" : [ ] ... Read More

Let us create a collection with documents −> db.demo590.insert([ ...    { "Name": "Chris", "Age": 21 }, ...    {"Name": "Bob", "Age": 20}, ...    { "Name": "Sam", "Age": 19 } ... ]); BulkWriteResult({    "writeErrors" : [ ],    "writeConcernErrors" : [ ],    "nInserted" : 3,    "nUpserted" : 0,    "nMatched" : 0,    "nModified" : 0,    "nRemoved" : 0,    "upserted" : [ ] })Display all documents from a collection with the help of find() method −> db.demo590.find();This will produce the following output −{ "_id" : ObjectId("5e92d514fd2d90c177b5bcd0"), "Name" : "Chris", "Age" : 21 } { ... Read More

To check equality and fetch the documents, use $where in MongoDB. Let us create a collection with documents −> db.demo589.insertOne({deliveryAddress:"US", billingAddress:"UK"});{    "acknowledged" : true, "insertedId" : ObjectId("5e92c117fd2d90c177b5bccc") } > db.demo589.insertOne({deliveryAddress:"US", billingAddress:"US"});{    "acknowledged" : true, "insertedId" : ObjectId("5e92c11bfd2d90c177b5bccd") } > db.demo589.insertOne({deliveryAddress:"US", billingAddress:"AUS"});{    "acknowledged" : true, "insertedId" : ObjectId("5e92c11ffd2d90c177b5bcce") } > db.demo589.insertOne({deliveryAddress:"UK", billingAddress:"US"});{    "acknowledged" : true, "insertedId" : ObjectId("5e92c127fd2d90c177b5bccf") }Display all documents from a collection with the help of find() method −> db.demo589.find();This will produce the following output −{ "_id" : ObjectId("5e92c117fd2d90c177b5bccc"), "deliveryAddress" : "US", "billingAddress" : "UK" } { "_id" : ObjectId("5e92c11bfd2d90c177b5bccd"), "deliveryAddress" : "US", "billingAddress" : ... Read More