You need to use some code in order to convert a string to numerical values in MongoDB.Let us first create a collection with a document. The query to create a collection with a document is as follows:> db.convertStringToNumberDemo.insertOne({"EmployeeId":"101", "EmployeeName":"Larry"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7f56528d10a061296a3c31") } > db.convertStringToNumberDemo.insertOne({"EmployeeId":"1120", "EmployeeName":"Mike"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7f56648d10a061296a3c32") } > db.convertStringToNumberDemo.insertOne({"EmployeeId":"3210", "EmployeeName":"Sam"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7f566e8d10a061296a3c33") }Display all documents from the collection with the help of find() method. The query is as follows −> db.convertStringToNumberDemo.find().pretty();The following is the output −{    "_id" ... Read More

The $unwind operator in MongoDB is the same for each array, it returns the mapping document. Here is the demo of $unwind operator in MongoDB.To understand the concept, let us create a collection with the document. The query to create a collection with a document is as follows −> db.unwindOperatorDemo.insertOne({"StudentName":"Larry", "StudentAge":23, "StudentSubje ct":["C", "C++", "Java", "MongoDB"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7ef5f3559dd2396bcfbfc8") }Display all documents from a collection with the help of find() method. The query is as follows −> db.unwindOperatorDemo.find().pretty();The following is the output −{    "_id" : ObjectId("5c7ef5f3559dd2396bcfbfc8"),    "StudentName" : "Larry",    "StudentAge" : ... Read More

You can use $all operator to find by multiple array items. To understand the concept, let us create a collection with the document.The query to create a collection with a document is as follows −> db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"John", "StudentLastName":"Smith",    "StudentCoreSubject":["Compiler", "Operating System", "Computer Networks"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7ef07b559dd2396bcfbfc4") } > db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"Carol", "StudentLastName":"Taylor",    "StudentCoreSubject":["MongoDB", "MySQL", "SQL Server"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7ef09d559dd2396bcfbfc5") } > db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"Bob", "StudentLastName":"Taylor",    "StudentCoreSubject":["MongoDB", "MySQL", "SQL Server"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7ef0c7559dd2396bcfbfc6") } > db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"David", "StudentLastName":"Johnson",    "StudentCoreSubject":["Compiler", "Operating System", "Computer Networks"]}); {   ... Read More

You can use $in operator to find with multiple array items. To understand the concept, let us create a collection with the document.The query to create a collection with a document is as follows −>db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"John", "StudentLastName":"Smith",    "StudentCoreSubject":["Compiler", "Operating System", "Computer Networks"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7ef07b559dd2396bcfbfc4") } >db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"Carol", "StudentLastName":"Taylor",    "StudentCoreSubject":["MongoDB", "MySQL", "SQL Server"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7ef09d559dd2396bcfbfc5") } >db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"Bob", "StudentLastName":"Taylor",    "StudentCoreSubject":["MongoDB", "MySQL", "SQL Server"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7ef0c7559dd2396bcfbfc6") } >db.findByMultipleArrayDemo.insertOne({"StudentFirstName":"David", "StudentLastName":"Johnson",    "StudentCoreSubject":["Compiler", "Operating System", "Computer Networks"]}); {    "acknowledged" : true,   ... Read More

You can use update() function to insert records in MongoDB if it does not exist. To understand the concept, let us create a collection with the document. The query to create a collection with a document is as follows −> db.insertIfNotExistsDemo.insertOne({"StudentName":"Mike", "StudentAge":21}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7eec7b559dd2396bcfbfc2") } > db.insertIfNotExistsDemo.insertOne({"StudentName":"Sam", "StudentAge":22}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7eec97559dd2396bcfbfc3") }Display all documents from a collection with the help of find() method. The query is as follows −> db.insertIfNotExistsDemo.find().pretty(); The following is the output: {    "_id" : ObjectId("5c7eec7b559dd2396bcfbfc2"),    "StudentName" : "Mike",    "StudentAge" : ... Read More

The syntax is as follows to rename a field for all documents. Here, we have used $renameLdb.yourCollectionName.update({}, {$rename:{"yourOldFieldName":"yourNewFieldName"}}, false, true);To understand the concept, let us create a collection with the document. The query to create a collection with a document is as follows −> db.renameFieldDemo.insertOne({"StudentName":"John"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7ee6c7559dd2396bcfbfbb") } > db.renameFieldDemo.insertOne({"StudentName":"Carol"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7ee6cb559dd2396bcfbfbc") } > db.renameFieldDemo.insertOne({"StudentName":"Bob"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7ee6cf559dd2396bcfbfbd") } > db.renameFieldDemo.insertOne({"StudentName":"David"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7ee6d3559dd2396bcfbfbe") } > db.renameFieldDemo.insertOne({"StudentName":"Maxwell"}); {    "acknowledged" : true,    "insertedId" ... Read More

You can use the aggregate framework to get a particular element from the MongoDB array. To understand the concept, let us create a collection with the document. The query to create a collection with the document is as follows −> db.getParticularElement.insertOne({"InstructorName":"Larry", "InstructorTechnicalSubject":["Java", "C", "C++", "MongoDB", "MySQL", "SQL Server"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c7ee027559dd2396bcfbfb1") }Display all documents from a collection with the help of find() method. The query is as follows −> db.getParticularElement.find().pretty();The following is the output −{    "_id" : ObjectId("5c7ee027559dd2396bcfbfb1"),    "InstructorName" : "Larry",    "InstructorTechnicalSubject" : [       "Java",       ... Read More

To get the storage size of a database in MongoDB, use the stats() method.At first, check the current database with the help of the following query −> db;The following is the output −testHere is the query to get the storage size of the database in MongoDB −> db.stats()The following is the output displaying the stats including the storage size −The following is the output −{    "db" : "test",    "collections" : 114,    "views" : 0,    "objects" : 391,    "avgObjSize" : 83.0076726342711,    "dataSize" : 32456,    "storageSize" : 3211264,    "numExtents" : 0,    "indexes" : 120,    "indexSize" : 2494464,    "fsUsedSize" : 126172377088,    "fsTotalSize" : 199229435904,    "ok" : 1 }

The following is the syntax to create MongoDB stored procedure −db.system.js.save (    {       _id:"yourStoredProcedueName",       value:function(argument1,....N)       {          statement1,          .          .          N       }    } );Now implement the above syntax. The query to create a stored procedure is as follows −> db.system.js.save (    {       _id:"addTwoValue",       value:function(a,b)       {          return a+b       }    } );The following is the output −WriteResult({ "nMatched" : 0, "nUpserted" : 1, "nModified" : 0, "_id" : "addTwoValue" })Now you can call the stored procedure using eval(). The query is as follows −> db.eval("return addTwoValue(100,25)"); 125

You can use positional operator $ for this. To understand the above concept, let us create a collection with the document. The query to create a collection with a document is as follows −> db.incrementValueInNestedArrayDemo.insertOne(    ... {"UniqueId":1,       ... "StudentDetails":       ... [          ... {             ... "StudentId":101,             ... "StudentMarks":97          ... },          ... {             ... "StudentId":103,             ... "StudentMarks":99     ... Read More