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
Count number of elements in an array with MongoDB?
To count number of elements in an array, use the aggregate framework. Let us first create a collection with documents −
>db.countNumberOfElementsDemo.insertOne({"UserMessage":["Hi","Hello","Bye","Awesome"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cef8ec2ef71edecf6a1f6a1")
}Display all documents from a collection with the help of find() method −
> db.countNumberOfElementsDemo.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5cef8ec2ef71edecf6a1f6a1"),
"UserMessage" : [
"Hi",
"Hello",
"Bye",
"Awesome"
]
}Following is the query to count number of elements in an array −
> db.countNumberOfElementsDemo.aggregate({$project: { NumberOfElements: { $size:"$UserMessage" }}})This will produce the following output −
{ "_id" : ObjectId("5cef8ec2ef71edecf6a1f6a1"), "NumberOfElements" : 4 }
Updated on: 30-Jul-2019
831 Views
Advertisements