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"}); ... 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,   ... 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":[ ...          { ...         ... Read More

Achieve this with aggregation pipeline. Let us first create a collection with documents −> db.demo413.insertOne( ...    { ...       "_id": "101", ...       "details": { ...          "Info1": { ...             Name:"Chris", ...         ... Read More

Let us create a collection with documents −> db.demo411.aggregate( ...    [ ...       {$project : { ...          _id : 0, ...          Information : {$map : {input : "$Information", as : "out", in : ["$$out.Name1", "$$out.Name2"]}} ...       ... Read More

Let us create a collection with documents −> db.demo411.insertOne( ...    { ...       "Information" : [ ...          { ...             "Name1" : "Chris", ...             "Name2" : "David" ...         ... 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: ... 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") ... 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}); ... Read More

For this, use $setIsSubset in MongoDB. Let us create a collection with documents −> db.demo407.insertOne( ...    { ...       Name:"Chris", ...       "details" : [ ...          { ...             id:100 ...          }, ... Read More