Difference between PostgreSQL and MongoDB

1. PostgreSQL (Object-Relational Database) :
PostgreSQL is a powerful, open source object-relational database management system (ORDBMS) with an emphasis on extensibility and standards compliance that uses and extends the SQL language combined with many features that safely store and scale the most complicated data workloads. PostgreSQL is ACID-compliant, transactional, that stores the data in the tabular format and uses constraints, triggers, roles, stored procedures and views as the core components. 

Why use PostgreSQL ?

• Free and open source.
• Available in multiple languages.
• Highly Extensible.
• Protects data integrity.
• Builds fault-tolerant environments.
• Robust access-control system
• Supports international characters.
• Apple uses PostgreSQL!

Writing queries in PostgreSQL: 

• Creating students table 
  

 CREATE TABLE students (id INT, name VARCHAR (100)); 

• Inserting a record into students table 
  

 INSERT INTO students VALUES (1, 'Geeks'); 

• Reading records from the students table 
  

 SELECT * FROM students; 

• Updating records in students table 
  

 UPDATE students SET name="GeeksforGeeks" WHERE id = 1; 

• Deleting records from students table 
  

 DELETE FROM students WHERE id = 1; 

2. MongoDB (Cross-platform Document-Oriented Database) : 
MongoDB is a NoSQL database where each record is a document comprising of key-value pairs that are similar to JSON objects with schemas. MongoDB is flexible and allows its users to create schema, databases, tables, etc. Documents that are identifiable by a primary key make up the basic unit of MongoDB. Once MongoDB is installed, users can make use of Mongo shell as well. Mongo shell provides a JavaScript interface through which the users can interact and carry out CRUD operations. 

In other words we can say that MongoDB is a general purpose, document-based, distributed database built for modern application developers and for the cloud era licensed under the Server Side Public License. 

Why use MongoDB? 

• Scalable and can serve several machines.
• It is JavaScript Based which makes it easier to use.
• Has Faster response because it is a document-oriented database.
• Simpler Environment Setup
• It uses JSON syntax which is very easy to use and has a wide range of browser compatibility.
• Data is stored in the form of JSON whether it is Objects, Object Members, Arrays, Values and Strings.
• Uber and Stack Companies uses MongoDB!

Writing queries in MongoDB: 

• Creating a student database 
  

 use student; 

• Creating a students table 
  

 db.createCollection("students"); 

• Inserting records into the students collection 
  

 db.students.insert 
(
    {
        "id" : 1,
        "Name" : "Harry",
                 "Team": "Geeks For Geeks"
    }
); 

• Reading from the students collection 
  

 db.students.find({Name : "Harry"}).forEach(printjson); 

Difference between PostgreSQL and MongoDB :

MongoDB	PostgreSQL
MongoDB was written in C++	PostgreSQL was written in C
MongoDB was started in 2007 by 10gen, which created the product based on the word humongous	PostgreSQL is an open-source project maintained by PostgreSQL Global Development Group and their prolific community
MongoDB offers the Community Support Forum, ServerFault, and StackOverflow. Users can also get enterprise support 24×7 via Enterprise grade support.	PostgreSQL has a wide variety of community and commercial support options available for users. The Community support includes mailing lists and IRC
Non-Relational Database Management System	Relational Database Management System
Document Oriented	Object Oriented
Only Available in English Language	Available in Multi Languages

Which is best and why? 

PostgreSQL is best when : You need Standard compliant, transactional and ACID (Atomicity, Consistency, Isolation and Durability) compliant out of the box which also has a wide support for NoSQL features. 

MongoDB is best when : You need Scalability and caching for real-time analytics but is not built for transactional data i.e., accounting systems.