Simply loop with forEach() and set column value from another column. Let us create a collection with documents −> db.demo51.insert({"Name1":"Chris", "Name":"David", "Age":24}); WriteResult({ "nInserted" : 1 }) > db.demo51.insert({"Name1":"Carol", "Name":"Mike", "Age":22}); WriteResult({ "nInserted" : 1 }) > db.demo51.insert({"Name1":"Sam", "Name":"Bob", "Age":26}); WriteResult({ "nInserted" : 1 })Display all documents from a collection with the help of find() method −> db.demo51.find();This will produce the following output −{ "_id" : ObjectId("5e27108ccfb11e5c34d8990d"), "Name1" : "Chris", "Name" : "David", "Age" : 24 } { "_id" : ObjectId("5e27108dcfb11e5c34d8990e"), "Name1" : "Carol", "Name" : "Mike", "Age" : 22 } { "_id" : ObjectId("5e27108ecfb11e5c34d8990f"), "Name1" : "Sam", "Name" : ... Read More

To avoid getting json array and get a value array, use $in. For greater than, use MongoDB $gt. Let us create a collection with documents −> db.demo50.save({"Value":40}); WriteResult({ "nInserted" : 1 }) > db.demo50.save({"Value":100}); WriteResult({ "nInserted" : 1 }) > db.demo50.save({"Value":20}); WriteResult({ "nInserted" : 1 }) > db.demo50.save({"Value":510}); WriteResult({ "nInserted" : 1 })Display all documents from a collection with the help of find() method −> db.demo50.find();This will produce the following output −{ "_id" : ObjectId("5e270c02cfb11e5c34d89903"), "Value" : 40 } { "_id" : ObjectId("5e270c05cfb11e5c34d89904"), "Value" : 100 } { "_id" : ObjectId("5e270c07cfb11e5c34d89905"), "Value" : 20 } { "_id" : ObjectId("5e270c11cfb11e5c34d89906"), "Value" ... Read More

To search for an array via id, use positional $ operator. For update, use the UPDATE in MongoDB. Let us create a collection with documents −> db.demo49.insertOne( ... { ... ...    "Name": "David", ...    "Details": [ ...       { ...          "_id": "D1234", ...          "Subject":"MySQL" ...       }, ...       { ...          "_id": "E234", ...          "Subject":"Java" ...       }, ...       { ...          "_id": "F456", ...       ... Read More

To get a specific number of items, use $slice operator in MongoDB. Let us create a collection with documents −> db.demo48.insertOne({"Name":["David", "Chris", "Sam", "Mike", "Carol"]}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e270491cfb11e5c34d89901") }Display all documents from a collection with the help of find() method −> db.demo48.find();This will produce the following output −{ "_id" : ObjectId("5e270491cfb11e5c34d89901"), "Name" : [ "David", "Chris", "Sam", "Mike", "Carol" ] }Following is the query to get only 2 items −> db.demo48.find({}, {Name:{$slice: 2}});This will produce the following output −{ "_id" : ObjectId("5e270491cfb11e5c34d89901"), "Name" : [ "David", "Chris" ] }Read More

To return the position of a document relative to the collection, use sort() along with count(). Let us create a collection with documents −> db.demo47.insertOne({"ClientName":"Adam"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e267240cfb11e5c34d898f0") } > db.demo47.insertOne({"ClientName":"John"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e267243cfb11e5c34d898f1") } > db.demo47.insertOne({"ClientName":"Chris"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e267247cfb11e5c34d898f2") } > db.demo47.insertOne({"ClientName":"Sam"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e26724ccfb11e5c34d898f3") }Display all documents from a collection with the help of find() method −> db.demo47.find();This will produce the following output −{ "_id" : ObjectId("5e267240cfb11e5c34d898f0"), "ClientName" : "Adam" } { "_id" : ... Read More

To index large text field, use ensureIndex() along with $regex for text search. Let us create a collection with documents −> db.demo46.ensureIndex({"Name":1}); {    "createdCollectionAutomatically" : true,    "numIndexesBefore" : 1,    "numIndexesAfter" : 2,    "ok" : 1 } > db.demo46.insertOne({"Name":"John Smith"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e267004cfb11e5c34d898ed") } > db.demo46.insertOne({"Name":"John Doe"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e267009cfb11e5c34d898ee") } > db.demo46.insertOne({"Name":"Chris Brown"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e267011cfb11e5c34d898ef") }Display all documents from a collection with the help of find() method −> db.demo46.find();This will produce the following output −{ "_id" : ... Read More

Let us first create a variable. Following is the query −> var studentDetails={"StudentFirstName":"Chris","StudentLastName":"Brown","StudentAge":24};Following is the query to save records using save() −> db.demo45.save(studentDetails); WriteResult({ "nInserted" : 1 })Display all documents from a collection with the help of find() method −> studentDetails;This will produce the following output −{    "StudentFirstName" : "Chris",    "StudentLastName" : "Brown",    "StudentAge" : 24,    "_id" : ObjectId("5e25dab4cfb11e5c34d898ec") }

For this, in a single query, simply work with forEach() and store output in a temp db. Let us first create a collection with documents −> db.demo43.insertOne({"StudentName":"Chris"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e25d4b3cfb11e5c34d898e5") } > db.demo43.insertOne({"StudentName":"Bob"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e25d4b8cfb11e5c34d898e6") } > db.demo43.insertOne({"StudentName":"David"}); {    "acknowledged" : true,    "insertedId" : ObjectId("5e25d4bbcfb11e5c34d898e7") }Display all documents from a collection with the help of find() method −> db.demo43.find();This will produce the following output −{ "_id" : ObjectId("5e25d4b3cfb11e5c34d898e5"), "StudentName" : "Chris" } { "_id" : ObjectId("5e25d4b8cfb11e5c34d898e6"), "StudentName" : "Bob" } { "_id" : ObjectId("5e25d4bbcfb11e5c34d898e7"), "StudentName" ... Read More

To rebuild indexes, use reIndex(). Let us first create an index. Following is the query −> db.demo42.createIndex({"StudentFirstName":1});This will produce the following output −{    "createdCollectionAutomatically" : true,    "numIndexesBefore" : 1,    "numIndexesAfter" : 2,    "ok" : 1 }Following is the query to rebuild index in MongoDB −> db.demo42.reIndex({"StudentFirstName":1});This will produce the following output −{    "nIndexesWas" : 2,    "nIndexes" : 2,    "indexes" : [       {          "v" : 2,          "key" : {             "_id" : 1          },          "name" : "_id_",          "ns" : "web.demo42"       },       {          "v" : 2,          "key" : {             "StudentFirstName" : 1          },          "name" : "StudentFirstName_1",          "ns" : "web.demo42"       }   ],    "ok" : 1 }

To perform multiple write operations, use bulkWrite(). Let us create an array list values. Following is the query −> const arrayList = [ ...    {"Value1":100, "Value2":200, "Name": "John"}, ...    {"Value1":100, "Value2":200, "Name": "Bob"} ... ]; > let op1 = []; > arrayList.forEach(({ Value1, Value2, Name }) => { ...    op1.push({ ...       "updateOne": { ...          "filter": { Name}, ...          "update": { "$set": { Value1, Value2, Name } }, ...          "upsert": true ...       } ...    }) ... }); > db.demo397.bulkWrite(op1); ... Read More