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To create index in the background, use createIndex() method and set “background: true” as in the below syntax −db.yourCollectionName.createIndex({"yourFieldName1":1,"yourFieldName2":1},{background: true} );Let us implement the above syntax in order to create index and set background −> db.indexCreationDemo.createIndex({"StudentName":1,"StudentAge":1},{background: true} ); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 }Let us display the indexes −> db.indexCreationDemo.getIndexes();This will produce the following output −[ { "v" : 2, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "web.indexCreationDemo" }, { "v" : 2, "key" : { "StudentName" : 1, "StudentAge" : 1 }, "name" : "StudentName_1_StudentAge_1", "ns" : "web.indexCreationDemo", "background" : true } ]
The collation introduced in version MongoDB 3.4. Maybe, you implemented collation in a previous version.For our example, we are using MongoDB version 4.0.5. Following is the query to check the current version on system −> db.version()This will produce the following output −4.0.5Let us first create a collection with documents −> db.collationExample.createIndex({Value: 1}, {collation: {locale: "en", strength: 1}}); { "createdCollectionAutomatically" : true, "numIndexesBefore" : 1, "numIndexesAfter" : 2, "ok" : 1 } > db.collationExample.insertOne({'Value':'x'}); { "acknowledged" : true, "insertedId" : ObjectId("5e038a3cf5e889d7a51994f5") } > db.collationExample.insertOne({'Value':'X'}); { "acknowledged" : true, "insertedId" : ObjectId("5e038a48f5e889d7a51994f6") } > ... Read More
To calculate average, use aggregate along with $avg. Let us first create a collection with documents −> db.calculateAverage.insertOne({'Value':[10, 20, 80]}); { "acknowledged" : true, "insertedId" : ObjectId("5e0383e3f5e889d7a51994dc") } > db.calculateAverage.insertOne({'Value':[12, 15, 16]}); { "acknowledged" : true, "insertedId" : ObjectId("5e0383edf5e889d7a51994dd") } > db.calculateAverage.insertOne({'Value':[30, 35, 40]}); { "acknowledged" : true, "insertedId" : ObjectId("5e0383f5f5e889d7a51994de") }Following is the query to display all documents from a collection with the help of find() method −> db.calculateAverage.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e0383e3f5e889d7a51994dc"), "Value" : [ 10, 20, ... Read More
To promote subfields to top level in projection, use $objectToArray and $arrayToObject. Let us first create a collection with documents:> db.promoteSubfieldsDemo.insertOne({'s':10, 'y':{'t':20, 'u':30, }}); { "acknowledged" : true, "insertedId" : ObjectId("5e038004190a577c668b55d5") }Following is the query to display all documents from a collection with the help of find() method −> db.promoteSubfieldsDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e038004190a577c668b55d5"), "s" : 10, "y" : { "t" : 20, "u" : 30 } }Following is the query to promote subfields to top level in projection without listing all keys ... Read More
To delete specific record, use “$pull” and since we are updating the already created collection, use UPDATE().Let us create a collection with documents −> db.demo213.insertOne({ ... "id": 101, ... "details1": [ ... { ... "Name": "Chris", ... "details2": [ ... { ... "StudentName": "David", ... "Subject": "MongoDB" ... }, ... { ... ... Read More
To find a MongoDB document through a word, use find() and set the word like −word/iLet us create a collection with documents −> db.demo212.insertOne({"details":[{"Name":"John Doe"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e3e2c7603d395bdc21346ff") } > db.demo212.insertOne({"details":[{"Name":"Chris Brown"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e3e2c8003d395bdc2134700") } > db.demo212.insertOne({"details":[{"Name":"Robert doe"}]}); { "acknowledged" : true, "insertedId" : ObjectId("5e3e2c8a03d395bdc2134701") }Display all documents from a collection with the help of find() method −> db.demo212.find();This will produce the following output −{ "_id" : ObjectId("5e3e2c7603d395bdc21346ff"), "details" : [ { "Name" : "John Doe" } ] } { "_id" : ObjectId("5e3e2c8003d395bdc2134700"), "details" : ... Read More
To test the values, use $type. Let us create a collection with documents −> db.demo211.insertOne({id:101, "Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e3e298203d395bdc21346fa") } > db.demo211.insertOne({id:102, "Name":null}); { "acknowledged" : true, "insertedId" : ObjectId("5e3e2a5403d395bdc21346fb") }Display all documents from a collection with the help of find() method −> db.demo211.find();This will produce the following output −{ "_id" : ObjectId("5e3e298203d395bdc21346fa"), "id" : 101, "Name" : "Chris" } { "_id" : ObjectId("5e3e2a5403d395bdc21346fb"), "id" : 102, "Name" : null }Following is the query to test if two external values are equal in a MongoDB criteria object −> v1=200; 200 > v2=200; ... Read More
To get the count of a specific value in MongoDB, use aggregate(). Let us create a collection with documents −> db.demo210.insertOne( ... { ... details: [ ... { ... ClientName: "Robert" ... }, ... { ... ... lientName: "John Doe" ... }, ... { ... ... ClientName: "Robert" ... }, ... { ... ... ... Read More
To convert filed value to create datetime day of month, use MongoDB aggregate(). Let us create a collection with documents −> db.demo209.insertOne( ... { ... "_id" : "101", ... "details" : [ ... { ... "dat" : 1528929908, ... "Name" : "Chris" ... }, ... { ... "dat" : 1529082069, ... "Name":"Carol" ... } ... ], ... ... Read More
To convert numeric string to number, use parseInt() in MongoDB. Let us create a collection with documents −> db.demo208.insertOne( { "value":"50"} ); { "acknowledged" : true, "insertedId" : ObjectId("5e3d92d803d395bdc21346f6") } > db.demo208.insertOne( { "value":"2350"} ); { "acknowledged" : true, "insertedId" : ObjectId("5e3d92dd03d395bdc21346f7") }Display all documents from a collection with the help of find() method −> db.demo208.find();This will produce the following output −{ "_id" : ObjectId("5e3d92d803d395bdc21346f6"), "value" : "50" } { "_id" : ObjectId("5e3d92dd03d395bdc21346f7"), "value" : "2350" }Following is the query to convert numeric string to number −> db.demo208.find().forEach( function (doc) { ... doc.value = parseInt(doc.value); ... Read More