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To fetch a specific document, use dot notation in MongoDB find(). Let us create a collection with documents −> db.demo672.insertOne({Brand:[{CategoryName:"Mobile", "Name":"Oppo"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5ea3ea9b04263e90dac943e5") } > db.demo672.insertOne({Brand:[{CategoryName:"Mobile", "Name":"Samsung"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5ea3eaa404263e90dac943e6") } > db.demo672.insertOne({Brand:[{CategoryName:"Mobile", "Name":"OnePlus"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5ea3eacc04263e90dac943e7") }Display all documents from a collection with the help of find() method −> db.demo672.find();This will produce the following output −{ "_id" : ObjectId("5ea3ea9b04263e90dac943e5"), "Brand" : [ { "CategoryName" : "Mobile", "Name" : "Oppo" } ] } { "_id" : ObjectId("5ea3eaa404263e90dac943e6"), "Brand" : [ { ... Read More
To get fields from multiple sub-documents, use MongoDB aggregate with $unwind. Let us create a collection with documents −> db.demo671.insertOne( ... { ... ... "details" : [ ... { ... "id" : "1" ... }, ... { ... CountryName:"US", ... "details1" : [ ... { ... "id" : "1" ... }, ... { ... "id" : "2" ... } ... ] ... ... Read More
To access subdocuments in MongoDB, use find() with dot notation. Let us create a collection with documents −> db.demo670.insertOne({ ... id:101, ... "details": ... { ... Name:"Chris", ... Age:21, ... CountryName:"US", ... SubjectName:"MongoDB" ... } ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5ea3e31d04263e90dac943de") } > db.demo670.insertOne({ id:102, "details": { Name:"David", Age:22, CountryName:"UK", SubjectName:"MySQL" } } ); { "acknowledged" : true, "insertedId" : ObjectId("5ea3e33604263e90dac943df") }Display all documents from a collection with the help of find() method −> db.demo670.find();This will produce the following output −{ "_id" : ObjectId("5ea3e31d04263e90dac943de"), "id" : 101, "details" : { "Name" ... Read More
To get the maximum element from the collection, sort in descending order with limit. Let us create a collection with documents −> > db.demo669.insertOne({"Marks":76}); { "acknowledged" : true, "insertedId" : ObjectId("5ea3133c04263e90dac943d9") } > db.demo669.insertOne({"Marks":55}); { "acknowledged" : true, "insertedId" : ObjectId("5ea3133f04263e90dac943da") } > db.demo669.insertOne({"Marks":89}); { "acknowledged" : true, "insertedId" : ObjectId("5ea3134204263e90dac943db") } > db.demo669.insertOne({"Marks":88}); { "acknowledged" : true, "insertedId" : ObjectId("5ea3134504263e90dac943dc") } > db.demo669.insertOne({"Marks":79}); { "acknowledged" : true, "insertedId" : ObjectId("5ea3134e04263e90dac943dd") }Display all documents from a collection with the help of find() method −> db.demo669.find();This will produce the following output ... Read More
Use $all for array match. The $all operator selects the documents where the value of a field is an array that contains all the specified elements. Let us create a collection with documents −> db.demo668.createIndex({"ListOfSubject":1}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.demo668.insert({"ListOfSubject":["MySQL", "Java", "C"]}); WriteResult({ "nInserted" : 1 }) > db.demo668.insert({"ListOfSubject":["MongoDB", "Python", "C++"]}); WriteResult({ "nInserted" : 1 }) > db.demo668.insert({"ListOfSubject":["C#", "Spring", "Hibernate", "MongoDB"]}); WriteResult({ "nInserted" : 1 })Display all documents from a collection with the help of find() method −> db.demo668.find();This will produce the following output −{ ... Read More
The ObjectId does not accept the seed string. You need to use _id − StringValue. Let us create a collection with documents −> db.demo667.insertOne({_id:"Chris"}); { "acknowledged" : true, "insertedId" : "Chris" } > db.demo667.insertOne({_id:"David"}); { "acknowledged" : true, "insertedId" : "David" } > db.demo667.insertOne({_id:"Chris"}); 2020-04-23T22:01:23.268+0530 E QUERY [js] WriteError: E11000 duplicate key error collection: test.demo667 index: _id_ dup key: { : "Chris" } : WriteError({ "index" : 0, "code" : 11000, "errmsg" : "E11000 duplicate key error collection: test.demo667 index: _id_ dup key: { : \"Chris\" }", "op" : { "_id" : ... Read More
To display only the employee names with specific salaries, set the salaries in MongoDB $in and fetch the names. Let us create a collection with documents> db.demo666.insertOne({"EmployeeName":"John", "EmployeeSalary":25000}); { "acknowledged" : true, "insertedId" : ObjectId("5ea1c04824113ea5458c7d0d") } > db.demo666.insertOne({"EmployeeName":"Chris", "EmployeeSalary":35000}); { "acknowledged" : true, "insertedId" : ObjectId("5ea1c05524113ea5458c7d0e") } > db.demo666.insertOne({"EmployeeName":"David", "EmployeeSalary":65000}); { "acknowledged" : true, "insertedId" : ObjectId("5ea1c06024113ea5458c7d0f") } > db.demo666.insertOne({"EmployeeName":"Carol", "EmployeeSalary":40000}); { "acknowledged" : true, "insertedId" : ObjectId("5ea1c06f24113ea5458c7d10") }Display all documents from a collection with the help of find() method −> db.demo666.find();This will produce the following output −{ "_id" : ObjectId("5ea1c04824113ea5458c7d0d"), "EmployeeName" ... Read More
To search for ranges, use sort() with limit(). Let us create a collection with documents −> db.demo665.insertOne({"Value":10}); { "acknowledged" : true, "insertedId" : ObjectId("5ea1bf1424113ea5458c7d08") } > db.demo665.insertOne({"Value":15}); { "acknowledged" : true, "insertedId" : ObjectId("5ea1bf1b24113ea5458c7d09") } > db.demo665.insertOne({"Value":55}); { "acknowledged" : true, "insertedId" : ObjectId("5ea1bf1e24113ea5458c7d0a") } > db.demo665.insertOne({"Value":25}); { "acknowledged" : true, "insertedId" : ObjectId("5ea1bf2324113ea5458c7d0b") } > db.demo665.insertOne({"Value":20}); { "acknowledged" : true, "insertedId" : ObjectId("5ea1bf2b24113ea5458c7d0c") }Display all documents from a collection with the help of find() method −> db.demo665.find();This will produce the following output −{ "_id" : ObjectId("5ea1bf1424113ea5458c7d08"), "Value" : 10 ... Read More
It is saved in the special system.js collection. For this, use db.system.js.save(). Following is the syntax −db.system.js.save({ _id: "anyFunctionName", value: function (returnValue) { return ‘yourMessage ' + returnValue; } })Let us implement the above syntax. Following is the query −> db.system.js.save({ ... _id: "returnValue", ... value: function (data) { ... return 'The value==== ' + data; ... } ... }) WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })Following is the query to call the above function to print the actual data −> db.eval("returnValue(20)") WARNING: db.eval is deprecatedThis will produce the following output −The value==== 20
To count number of documents, use count() in MongoDB. Let us create a collection with documents −> db.demo664.insertOne({_id:1, ClientName:"Chris"}); { "acknowledged" : true, "insertedId" : 1 } > db.demo664.insertOne({_id:2, ClientName:"Bob"}); { "acknowledged" : true, "insertedId" : 2 } > db.demo664.insertOne({_id:3, ClientName:"Sam"}); { "acknowledged" : true, "insertedId" : 3 } > db.demo664.insertOne({_id:4, ClientName:"David"}); { "acknowledged" : true, "insertedId" : 4 }Display all documents from a collection with the help of find() method −> db.demo664.find();This will produce the following output −{ "_id" : 1, "ClientName" : "Chris" } { "_id" : 2, "ClientName" : "Bob" } { "_id" : 3, "ClientName" : ... Read More