To get array of nested string in MongoDB, use dot notation in find(). Let us create a collection with documents −> db.demo89.insertOne( ... { id: 101, Details: [ { Name: "Chris", Marks: 45 }, { Name: "David", Marks: 55, Subjects : ["MySQL", "MongoDB", "Java", "C"] } ] ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2c163b79799acab037af51") } > db.demo89.insertOne( ... { id: 102, Details: [ { Name: "Mike", Marks: 48 }, { Name: "Bob", Marks: 98, Subjects : ["C++", "MySQL"] } ] ... } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2c163c79799acab037af52") }Display ... Read More

Yes, you can use $indexOfCP to use a filed value as a pattern. Let us create a collection with documents −> db.demo88.insertOne( ...    { ...       "Name": "Chris", ...       "PassoutYear": "2020", ...       "websiteName": "chris.shop.com/Carol-2020-" ...    } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2c14c471bf0181ecc422b1") } > db.demo88.insertOne( ...    { ...       "Name": "David", ...       "PassoutYear": "2010", ...       "websiteName": "david.bigshop.com/David-2010-" ...    } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2c14c571bf0181ecc422b2") }Display all documents from a ... Read More

To filter by several array elements, use $elemMatch. Let us create a collection with documents −> db.demo87.insertOne( ...    { ...       id:101, ...       "Details": [ ...          { ...             "EmployeeName": "Chris", ...             "Salary": 45000 ...          }, ...          { ...             "EmployeeName": "David", ...             "Salary": 50000 ...       } ...    ] ... } ... ); {    "acknowledged" ... Read More

For this, use $not along with $in. Let us create a collection with documents −[    {       id: "101",       subjectid: [          "102"       ]    },    {       id: "102",       subjectid: [          "102"       ]    } ]Here is the snapshot.Display all documents from a collection with the help of find() method −db.collection.find()This will produce the following output −[    {       "_id": ObjectId("5a934e000102030405000000"),       "id": "101",       "subjectid": [          "102"       ]    },    {       "_id": ObjectId("5a934e000102030405000001"),       "id": "102",       "subjectid": [          "102"       ]    } ]Following is the query that uses $expr, $not and $in to fetch values excluding matching field array value −db.collection.find({    $expr: {       $not:{          $in: [             "$id",             "$subjectid"          ]       }    } })This will produce the following output −[    {       "_id": ObjectId("5a934e000102030405000000"),       "id": "101",       "subjectid": [          "102"       ]    } ]

To match multiple criteria inside an array, use aggregate(). Let us create a collection with documents −> db.demo84.insertOne({ ...    "EmployeeDetails": [ ...       {Name: 'John', Salary:45000, isMarried: true}, ...       {Name: 'Chris', Salary:50000, isMarried: false} ...       ] ...    } ... ); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2c0a3471bf0181ecc422a5") } > db.demo84.insertOne({ ...    "EmployeeDetails": [ ...       {Name: 'Sam', Salary:56000, isMarried: false}, ...       {Name: 'Bob', Salary:50000, isMarried: false} ...       ] ...    } ... ); {    "acknowledged" : true,   ... Read More

To fetch a document, use $in, instead of $and in MongoDB. Let us first create a collection with documents −> db.demo83.insertOne( ... { ...    "Details":[ ...       { ...          "Name":"Chris", ...          "Subject":[ ...             "MySQL", ...             "MongoDB" ...          ] ...       }, ...       { ...          "Name":"David", ...          "Subject":[ ...          "Java", ...          "C" ... ... Read More

To make a unique field in MongoDB, use unique − true. Let us create a collection with documents −> db.demo82.createIndex({"EmployeeName":1}, {unique:true}); {    "createdCollectionAutomatically" : true,    "numIndexesBefore" : 1,    "numIndexesAfter" : 2,    "ok" : 1 } > db.demo82.insertOne({"EmployeeName":"Chris"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2bfb1b71bf0181ecc422a0") } > db.demo82.insertOne({"EmployeeName":"David"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2bfb1f71bf0181ecc422a1") } > db.demo82.insertOne({"EmployeeName":"Chris"}); 2020-01-25T13:54:00.410+0530 E QUERY [js] WriteError: E11000 duplicate key error collection: test.demo82 index: EmployeeName_1 dup key: { : "Chris" } : WriteError({    "index" : 0,    "code" : 11000,    "errmsg" : "E11000 duplicate key ... Read More

To get a specific item in a sudocument, use the dot(.) notation. Let us create a collection with documents −> db.demo81.insertOne({"StudentDetails":[{"StudentName":"Carol", "StudentSubject":"Java"}, { "StudentName" : "David", "StudentSubject" : "MongoDB" }]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2bf6ec71bf0181ecc4229d") } > db.demo81.insertOne({"StudentDetails":[{"StudentName":"Mike", "StudentSubject":"Python"}, { "StudentName" : "David", "StudentSubject" : "C" }]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2bf70471bf0181ecc4229e") } > db.demo81.insertOne({"StudentDetails":[{"StudentName":"Jace", "StudentSubject":"C++"}, {    "StudentName" : "John", "StudentSubject" : "MySQL" }]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2bf72071bf0181ecc4229f") }Display all documents from a collection with the help of find() method −> db.demo81.find();This will produce the following ... Read More

To calculate average in MongoDB, use $avg. Let us create a collection with documents −> db.demo80.insertOne({"Details":{"Price":10.5}}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2bf43271bf0181ecc42297") } > db.demo80.insertOne({"Details":{"Price":50.3}}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2bf43871bf0181ecc42298") } > db.demo80.insertOne({"Details":{"Price":100.10}}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2bf43f71bf0181ecc42299") }Display all documents from a collection with the help of find() method −> db.demo80.find();This will produce the following output −{ "_id" : ObjectId("5e2bf43271bf0181ecc42297"), "Details" : { "Price" : 10.5 } } { "_id" : ObjectId("5e2bf43871bf0181ecc42298"), "Details" : { "Price" : 50.3 } } { "_id" : ObjectId("5e2bf43f71bf0181ecc42299"), "Details" : { "Price" ... Read More

Let us create a collection with documents −> db.demo78.insertOne({"Name1":"Chris", "Name2":"Mike"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2bd99c71bf0181ecc4228f") } > db.demo78.insertOne({"Name1":"Bob", "Name2":"Carol"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2bd9ac71bf0181ecc42290") } > db.demo78.insertOne({"Name1":"David", "Name2":"Sam"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2bd9b671bf0181ecc42291") } > db.demo78.insertOne({"Name1":"Jace", "Name2":"John"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e2bd9bf71bf0181ecc42292") }Display all documents from a collection with the help of find() method −> db.demo78.find();This will produce the following output −{ "_id" : ObjectId("5e2bd99c71bf0181ecc4228f"), "Name1" : "Chris", "Name2" : "Mike" } { "_id" : ObjectId("5e2bd9ac71bf0181ecc42290"), "Name1" : "Bob", "Name2" : "Carol" } { ... Read More