- Trending Categories
- Data Structure
- Networking
- RDBMS
- Operating System
- Java
- MS Excel
- iOS
- HTML
- CSS
- Android
- Python
- C Programming
- C++
- C#
- MongoDB
- MySQL
- Javascript
- PHP
- Physics
- Chemistry
- Biology
- Mathematics
- English
- Economics
- Psychology
- Social Studies
- Fashion Studies
- Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Found 6702 Articles for Database
79 Views
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
217 Views
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
459 Views
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
132 Views
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
213 Views
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") }
582 Views
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
475 Views
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 }
161 Views
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
2K+ Views
For this, use $lookup. This performs a left outer join to an unsharded collection in the same database to filter in documents from the “joined” collection for processing.Let us first create a collection with documents −> db.demo395.insertOne({Name:"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e5e782317aa3ef9ab8ab207") } > db.demo395.insertOne({Name:"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e5e782317aa3ef9ab8ab208") }Display all documents from a collection with the help of find() method −> db.demo395.find();This will produce the following output −{ "_id" : ObjectId("5e5e782317aa3ef9ab8ab207"), "Name" : "Chris" } { "_id" : ObjectId("5e5e782317aa3ef9ab8ab208"), "Name" : "David" }Let us create a second collection with documents ... Read More
160 Views
Let us first create a collection with documents −> db.demo394.insertOne( ... { ... ... details: [ ... { ... _id: '1', ... startDate: '2018-01-11T07:00:00.000Z', ... endDate: '2019-01-12T07:59:59.999Z' ... }, ... { ... _id: '2', ... startDate: '2019-01-21T07:00:00.000Z', ... endDate: '2020-01-04T07:59:59.999Z' ... } ... ] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e5e716817aa3ef9ab8ab202") }Display all ... Read More