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Let us first create a collection with documents −> db.demo417.insertOne({"EmployeeName":"Chris", "EmployeeSalary":500}); { "acknowledged" : true, "insertedId" : ObjectId("5e723ebbb912067e57771ae4") } > db.demo417.insertOne({"EmployeeName":"Mike", "EmployeeSalary":1000}); { "acknowledged" : true, "insertedId" : ObjectId("5e723ed7b912067e57771ae5") }Display all documents from a collection with the help of find() method −> db.demo417.find();This will produce the following output −{ "_id" : ObjectId("5e723ebbb912067e57771ae4"), "EmployeeName" : "Chris", "EmployeeSalary" : 500 } { "_id" : ObjectId("5e723ed7b912067e57771ae5"), "EmployeeName" : "Mike", "EmployeeSalary" : 1000 }Following is the query to update salary field value with 10 percent of each employee in employee collection −> db.demo417.update({ "EmployeeName": { $in: ["Chris", "Mike"] } }, ... Read More
To convert collection to capped, use runCommand(). It provides a helper to run specified database commands. Let us first create a collection with documents −> db.demo416.insertOne({"StudentName":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e723a7bb912067e57771adf") } > db.demo416.insertOne({"StudentName":"Mike"}); { "acknowledged" : true, "insertedId" : ObjectId("5e723a81b912067e57771ae0") } > db.demo416.insertOne({"StudentName":"Sam"}); { "acknowledged" : true, "insertedId" : ObjectId("5e723a84b912067e57771ae1") }Display all documents from a collection with the help of find() method −> db.demo416.find();This will produce the following output −{ "_id" : ObjectId("5e723a7bb912067e57771adf"), "StudentName" : "David" } { "_id" : ObjectId("5e723a81b912067e57771ae0"), "StudentName" : "Mike" } { "_id" : ObjectId("5e723a84b912067e57771ae1"), "StudentName" : ... Read More
To select specific columns, you can ignore the rest of them i.e. to hide those columns, set them to 0. Let us first create a collection with documents −> db.demo415.insertOne({"ClientName":"Robert", "ClientCountryName":"US"}); { "acknowledged" : true, "insertedId" : ObjectId("5e72329db912067e57771adc") } > db.demo415.insertOne({"ClientName":"David", "ClientCountryName":"UK"}); { "acknowledged" : true, "insertedId" : ObjectId("5e7232acb912067e57771add") } > db.demo415.insertOne({"ClientName":"Bob", "ClientCountryName":"AUS"}); { "acknowledged" : true, "insertedId" : ObjectId("5e7232b4b912067e57771ade") }Display all documents from a collection with the help of find() method −> db.demo415.find();This will produce the following output −{ "_id" : ObjectId("5e72329db912067e57771adc"), "ClientName" : "Robert", "ClientCountryName" : "US" } { "_id" : ObjectId("5e7232acb912067e57771add"), ... Read More
To find by _id on an array of objects, use aggregation and avoid using find(). Let us first create a collection with documents −> db.demo414.insertOne( ... { ... "_id": "110", ... "details":[ ... { ... "StudentName":"John", ... "StudentMarks":56 ... }, ... { ... "StudentName":"Robert", ... "StudentMarks":98 ... } ... ] ... } ... ); { "acknowledged" : true, "insertedId" : "110" }Display all documents from a collection with the help of find() method −> db.demo414.find();This will produce the following output −{ "_id" : "110", "details" : [ { "StudentName" : "John", "StudentMarks" : 56 }, { "StudentName" : "Robert", "StudentMarks" : 98 } ] }Following is the query to find by _id on an array of objects −> db.demo414.aggregate([{$unwind: "$details"}, {$match:{"details.StudentMarks" :56}}] )This will produce the following output −{ "_id" : "110", "details" : { "StudentName" : "John", "StudentMarks" : 56 } }
Achieve this with aggregation pipeline. Let us first create a collection with documents −> db.demo413.insertOne( ... { ... "_id": "101", ... "details": { ... "Info1": { ... Name:"Chris", ... Age:21 ... }, ... "Info2": { ... Name:"David", ... Age:23 ... } ... } ... } ... ); { "acknowledged" : true, "insertedId" : "101" }Display all documents from a collection with the help of find() method −> db.demo413.find();This will produce the following output −{ "_id" : "101", "details" : { "Info1" : { "Name" : "Chris", "Age" : 21 }, "Info2" : { "Name" : "David", "Age" : 23 } } }Following is the query to exclude nested fields −> db.demo413.aggregate([ ... { $project: { "details" : { $objectToArray: "$details" } } }, ... { $project: { "details.v.Age" : 0} }, ... { $project: { "details" : { $arrayToObject: "$details"} } } ... ]);This will produce the following output −{ "_id" : "101", "details" : { "Info1" : { "Name" : "Chris" }, "Info2" : { "Name" : "David" } } }
Let us create a collection with documents −> db.demo411.aggregate( ... [ ... {$project : { ... _id : 0, ... Information : {$map : {input : "$Information", as : "out", in : ["$$out.Name1", "$$out.Name2"]}} ... } ... } ... ] ... ) { "Information" : [ [ "Chris", "David" ], [ "John", "John" ] ] } > db.demo412.insertOne( ... { ... "Information1" : [ ... { ... ... Read More
Let us create a collection with documents −> db.demo411.insertOne( ... { ... "Information" : [ ... { ... "Name1" : "Chris", ... "Name2" : "David" ... }, ... { ... "Name1" : "John", ... "Name2" : "John" ... } ... ] ... } ... ); { "acknowledged" : true, "insertedId" ... Read More
To remove elements, use $pull and for such conditions, use $ne. The $ne in MongoDB is used to select the documents where the value of the field is not equal to the specified value.Let us create a collection with documents −> db.demo410.insertOne( ... { ... details: [{isMarried:false}, {isMarried:true}, {isMarried:false}, {isMarried:"Chris"}] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e70efc515dc524f70227681") }Display all documents from a collection with the help of find() method −> db.demo410.find();This will produce the following output −{ "_id" : ObjectId("5e70efc515dc524f70227681"), "details" : [ { "isMarried" : false }, { ... Read More
To find documents with a specific string, use find() and in that search for a string with regex. Let us create a collection with documents −> db.demo409.insertOne({"Name":"John Doe"}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e4e515dc524f7022767c") } > db.demo409.insertOne({"Name":"Chris Brown"}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e4ec15dc524f7022767d") } > db.demo409.insertOne({"Name":"Robert Doe"}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e4f415dc524f7022767e") } > db.demo409.insertOne({"Name":"David Brown"}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e4fe15dc524f7022767f") }Display all documents from a collection with the help of find() method −> db.demo409.find();This will produce the following output −{ "_id" : ObjectId("5e70e4e515dc524f7022767c"), "Name" ... Read More
To get a query plan in MongoDB, use explain(). The $explain operator gives information on the query plan.Let us create a collection with documents −> db.demo408.insertOne({"Value":50}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e3a115dc524f70227678") } > db.demo408.insertOne({"Value":20}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e3a715dc524f70227679") } > db.demo408.insertOne({"Value":45}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e3ac15dc524f7022767a") } > db.demo408.insertOne({"Value":35}); { "acknowledged" : true, "insertedId" : ObjectId("5e70e3af15dc524f7022767b") } > db.demo408.createIndex({Value:1}); { "createdCollectionAutomatically" : false, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 }Display all documents from a collection with the help ... Read More