- 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
134 Views
To filter the logs containing the word “work” , use aggregate() along with $filter. Let us first create a collection with documents −> db.demo383.insertOne( ... { ... "ServerName":"Jboss", ... "ServerLogs": [ ... { ... "status":"Working" ... }, ... { ... "status":"Stop" ... }, ... { ... "status":"Worked" ... } ... ... Read More
357 Views
For this, use $project and in that, $size to get the length. Let us first create a collection with documents −> db.demo382.insertOne( ... { ... ... "Name" : "David", ... "details" : [ ... { ... "SubjectName":"MySQL" ... }, ... { ... "SubjectName":"MongoDB" ... }, ... { ... "SubjectName":"Java" ... } ... Read More
500 Views
For this, use $indexOfArray. Let us first create a collection with documents −> db.demo381.insertOne({"Values":[10, 40, 60, 30, 60]}); { "acknowledged" : true, "insertedId" : ObjectId("5e5b59f72ae06a1609a00b15") } > db.demo381.insertOne({"Values":[100, 500, 700, 500, 800]}); { "acknowledged" : true, "insertedId" : ObjectId("5e5b59f72ae06a1609a00b16") } > db.demo381.insertOne({"Values":[20, 40, 30, 10, 60]}); { "acknowledged" : true, "insertedId" : ObjectId("5e5b59f72ae06a1609a00b17") }Display all documents from a collection with the help of find() method −> db.demo381.find();This will produce the following output −{ "_id" : ObjectId("5e5b59f72ae06a1609a00b15"), "Values" : [ 10, 40, 60, 30, 60 ] } { "_id" : ObjectId("5e5b59f72ae06a1609a00b16"), "Values" : [ 100, ... Read More
964 Views
The $addToSet operator adds a value to an array unless the value is already present, in which case $addToSet does nothing to that array.Let us first create a collection with documents −> db.demo380.insertOne({ ... ... "details" : [ ... { ... "Name" : "Chris", ... "details1" : [ ] ... }, ... { ... "Name" : "David", ... "details1" : [ ] ... } ... ] ... } ... ); ... Read More
929 Views
For projection on specific nested properties, use aggregate() in MongoDB. Let us first create a collection with documents −> db.demo379.insertOne( ... { ... "details1" : { ... "details2" : { ... "details3" : { ... "10" : "John", ... "50" : "Chris", ... "40" : "David", ... "30":"Mike" ... } ... ... Read More
144 Views
To manipulate subdocuments, use dot(.) notation in MongoDB. Let us first create a collection with documents −> db.demo378.insertOne( ... { ... Name: 'Chris', ... details:[ ... {id:101, Score:56}, ... {id:102, Score:78} ... ] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e5a758a2ae06a1609a00b0f") }Display all documents from a collection with the help of find() method −> db.demo378.find();This will produce the following output −{ "_id" : ObjectId("5e5a758a2ae06a1609a00b0f"), "Name" : "Chris", "details" : [ { "id" ... Read More
314 Views
To concatenate, use $concat in MongoDB aggregate(). Let us first create a collection with documents −> db.demo377.insertOne({"ListOfIds":[1001, 1002, 1003, 1004, 1005, 1006, 1007]}); { "acknowledged" : true, "insertedId" : ObjectId("5e5a73462ae06a1609a00b0e") }Display all documents from a collection with the help of find() method −> db.demo377.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e5a73462ae06a1609a00b0e"), "ListOfIds" : [ 1001, 1002, 1003, 1004, 1005, 1006, 1007 ] }Following is the query to concatenate an array of integer ... Read More
573 Views
To update documents, you cannot use aggregation pipeline. You can use update(). Let us first create a collection with documents −> db.demo376.insertOne( ... { ... ... "id" :101, ... ... "details" : [ ... { ... Name:"Chris", ... Age:21, ... Score:45 ... }, ... { ... Name:"David", ... Age:23, ... ... Read More
481 Views
JavaScript function can be saved for reuse using a system collection called system.js. To store a function, use the db.collection.save(),Let us first create a function. Following is the query −> db.system.js.save({ ... _id: "displayMessage", ... value: function (data) { ... return 'The Name is: ' + data; ... } ... })This will produce the following output −WriteResult({ "nMatched" : 0, "nUpserted" : 1, "nModified" : 0, "_id" : "displayMessage" })Following is the query to execute stored function −> db.eval("displayMessage('John')") WARNING: db.eval is deprecatedThis will produce the following output −The Name is: John
233 Views
There is no difference between show dbs and show databases. Both commands internally call listDatabases command.The show dbs command is as follows −> show dbsThis will produce the following output −admin 0.002GB app 0.000GB business 0.000GB config 0.000GB local 0.000GB main 0.000GB ... Read More