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
Return True if a document exists in MongoDB?
Let us first create a collection. Following is the query to create a collection with documents
> db.documentExistsOrNotDemo.insertOne({"UserId":101,"UserName":"John"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9932bd330fd0aa0d2fe4cf")
}
> db.documentExistsOrNotDemo.insertOne({"UserId":102,"UserName":"Chris"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9932c6330fd0aa0d2fe4d0")
}
> db.documentExistsOrNotDemo.insertOne({"UserId":102,"UserName":"Robert"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c9932ce330fd0aa0d2fe4d1")
}Following is the query to display all the documents from a collection with the help of find() method
> db.documentExistsOrNotDemo.find().pretty();
This will produce the following output
{
"_id" : ObjectId("5c9932bd330fd0aa0d2fe4cf"),
"UserId" : 101,
"UserName" : "John"
}
{
"_id" : ObjectId("5c9932c6330fd0aa0d2fe4d0"),
"UserId" : 102,
"UserName" : "Chris"
}
{
"_id" : ObjectId("5c9932ce330fd0aa0d2fe4d1"),
"UserId" : 102,
"UserName" : "Robert"
}Case 1: Following is the query that returns true if a document exists
> db.documentExistsOrNotDemo.find({"UserId":101}).count() > 0;This will produce the following output
True
Case 2 Following is the query that returns false if a document does not exist
> db.documentExistsOrNotDemo.find({"UserId":110}).count() > 0;This will produce the following output
False
Updated on: 30-Jul-2019
3K+ Views
Advertisements