Yes, to query for a field in an object in the array with MongoDB, use the following syntax −db.yourCollectionName.find({"yourOuterFieldName": { $elemMatch: { "yourInnerFieldName": "yourValue" } } } ).pretty();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.objectInAnArrayDemo.insertOne({ "StudentDetails": [{    "StudentName": "John", "StudentMessage": "Hi"}, {"StudentName": "Larry", "StudentMessage": "Hello"}]}) {    "acknowledged" : true,    "insertedId" : ObjectId("5c92635d36de59bd9de06381") } > db.objectInAnArrayDemo.insertOne({ "StudentDetails": [{    "StudentName": "Carol", "StudentMessage": "Hello"}, {"StudentName": "David", "StudentMessage": "Good Morning"}]}) {    "acknowledged" : true,    "insertedId" : ObjectId("5c92637936de59bd9de06382") }Display all documents ... Read More

You can use printjson() method to print to console an object in a MongoDB script. The syntax is as follows −printjson({yourFieldName”:yourValue”, ........N});You can use JSON.stringify() along with print() function. The syntax is as follows minus;print ( JSON.stringify( { {yourFieldName”:yourValue”, ........N} } ));Let us implement the above syntax to print object in Mongo script. The query is as follows −>printjson({"UserId":101, "UserName":"John", "UserCoreSuject":["Java", "MongoDB", "MySQL", "SQL Server"]});The following is the output −{    "UserId" : 101,    "UserName" : "John",    "UserCoreSuject" : [       "Java",       "MongoDB",       "MySQL",       "SQL Server"   ... Read More

To retrieve a value from MongoDB by its key name, use the following syntax −db.yourCollectionName.find({}, {"yourFieldName":1}).pretty();To understand the above syntax, let us create a collection with the document. The query to create a collection with a document is as follows −> db.retrieveValueFromAKeyDemo.insertOne({"CustomerName":"Larry", "CustomerAge":21, "CustomerCountryName":"US"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c9163b5a56efcc0f9e69048") } > db.retrieveValueFromAKeyDemo.insertOne({"CustomerName":"Chris", "CustomerAge":24, "CustomerCountryName":"AUS"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c9163c4a56efcc0f9e69049") } > db.retrieveValueFromAKeyDemo.insertOne({"CustomerName":"Mike", "CustomerAge":26, "CustomerCountryName":"UK"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c9163d3a56efcc0f9e6904a") }Display all documents from a collection with the help of find() method. The query is as follows −> db.retrieveValueFromAKeyDemo.find().pretty();The ... Read More

In order to delete the collection which has some special characters like _ or -, you need to use the following syntax −db.getCollection("yourCollectionName").drop();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.createCollection("_personalInformation"); { "ok" : 1 } > db.getCollection('_personalInformation').insertOne({"ClientName":"Chris", "ClientCountryName":"US"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c9158bb4afe5c1d2279d6b2") } > db.getCollection('_personalInformation').insertOne({"ClientName":"Mike", "ClientCountryName":"UK"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c9158c84afe5c1d2279d6b3") } > db.getCollection('_personalInformation').insertOne({"ClientName":"David", "ClientCountryName":"AUS"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c9158d54afe5c1d2279d6b4") }Display all documents from a collection with the ... Read More

To remove the _id element, you can use the following syntax −db.yourCollectionName.find({}, {'_id': false}).pretty();To understand the above syntax, let us create a collection with the document. The query to create a collection with a document is as follows −> db.removingidElementDemo.insertOne({"UserName":"John", ... "UserAge":21}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c9153fd4afe5c1d2279d6ad") } > db.removingidElementDemo.insertOne({"UserName":"Carol", "UserAge":24}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c9154084afe5c1d2279d6ae") } > db.removingidElementDemo.insertOne({"UserName":"David", "UserAge":22}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c9154154afe5c1d2279d6af") } > db.removingidElementDemo.insertOne({"UserName":"Mike", "UserAge":26}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c9154204afe5c1d2279d6b0") } > db.removingidElementDemo.insertOne({"UserName":"Chris", "UserAge":20}); {    "acknowledged" : true,   ... Read More

There is no in-built function to count a number of keys in a document. In order to count a number of keys, you need to write some code.Let us create a collection with a document. The query to create a collection with a document is as follows −> db.numberofKeysInADocumentDemo.insertOne({    "UserName":"John", "UserAge":21, "UserEmailId":"john12@gmail.com", "UserCountryName":"US"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c9132584afe5c1d2279d6ac") }Display all documents from a collection with the help of find() method. The query is as follows −> db.numberofKeysInADocumentDemo.find().pretty();The following is the output −{    "_id" : ObjectId("5c9132584afe5c1d2279d6ac"),    "UserName" : "John",    "UserAge" : 21,   ... Read More

You can use “$regex” operator to implement the equivalent of SQL ‘like’ in MongoDB. To implement it, let us create a collection with a document. The query to create a collection with a document is as follows −> db.sqlLikeDemo.insertOne({"UserName":"John Smith", "UserAge":24}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c912e124afe5c1d2279d6a5") } > db.sqlLikeDemo.insertOne({"UserName":"John Doe", "UserAge":21}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c912e264afe5c1d2279d6a6") } > db.sqlLikeDemo.insertOne({"UserName":"Chris Williams", "UserAge":22}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c912e404afe5c1d2279d6a7") } > db.sqlLikeDemo.insertOne({"UserName":"Robert Taylor", "UserAge":26}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c912e4d4afe5c1d2279d6a8") } > db.sqlLikeDemo.insertOne({"UserName":"John Brown", "UserAge":27}); {    "acknowledged" ... Read More

PyMongo is a Python distribution containing tools for working with MongoDB. Use the following syntax to use a variable for collection name −var yourVariableName="yourCollectionName"; db[storeCollectionName].yourOperationName;To understand the above syntax, let us create a collection with the document. The query to create a collection with a document is as follows. We have used variable for collection name −> var storeCollectionName="new_Collection"; > db[storeCollectionName].insertOne({"UserName":"John", "UserAge":21}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c912aea4afe5c1d2279d6a0") } > db[storeCollectionName].insertOne({"UserName":"Carol", "UserAge":24}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c912af54afe5c1d2279d6a1") } > db[storeCollectionName].insertOne({"UserName":"Mike", "UserAge":27}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c912afe4afe5c1d2279d6a2") }Display ... Read More

To get the database data size in MongoDB, you can use stats() method. The syntax is as follows −db.stats();Let us use the database with the name ‘test’.Now, check the current database with the help of the following query −> db;The following is the output −testHere is the query to get database data size in MongoDB −> db.stats()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" ... Read More

To find a document with Objectid in MongoDB, use the following syntax −db.yourCollectionName.find({"_id":ObjectId("yourObjectIdValue")}).pretty();To understand the above syntax, let us create a collection with the document. The query to create a collection with a document is as follows −> db.findDocumentWithObjectIdDemo.insertOne({"UserName":"Larry"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c90e4384afe5c1d2279d69b") } > db.findDocumentWithObjectIdDemo.insertOne({"UserName":"Mike", "UserAge":23}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c90e4444afe5c1d2279d69c") } > db.findDocumentWithObjectIdDemo.insertOne({"UserName":"Carol", "UserAge":26, "UserHobby":["Learning", "Photography"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5c90e4704afe5c1d2279d69d") }Display all documents from a collection with the help of find() method. The query is as follows −> db.findDocumentWithObjectIdDemo.find().pretty();The following is the output ... Read More