Indexes comparison between MongoDB and MS SQL Server.

A database index is a data structure that improves the speed of data retrieval operations. Indexes are necessary for high performance read operations for frequently used queries. Without indexes, database table/collection will be scanned fully to select required data that match the query statement. Full database table/collection scan is very slow operation for a huge amount of data. But indexes can increase read operation performance to point to exact records without necessity to scan all the records in storage.
Indexes are very useful and essential for database storage at the cost of additional storage space and influence on write/update/delete operations speed.
Fundamentally, indexes in MS SQL Server and MongoDB are similar. But, of course there are a couple of differences between them. 


The base difference between SQL and NoSQL databases. MS SQL Server vs. MongoDB.

If there is no real reason to resign from SQL database do not do this. This is the main rule J.

The main reason why you can ask youself why you need to move to NoSQL databases are necessity in huge very huge data storage (in other words Big Data), scalability and performance reasons.

But, you can ask yourself, what is the difference between them? Why I have to use one instead of another? The table below contains the brief difference explanation. More details beneath in the article.Relational databases were developed in 1970s. It was very courteous way to store data and satisfied those day needs. But today, relational databases are not able to solve the needs of the current scope for storing gigantic data. NoSQL technic for storing data is a substitute for solving the nowadays needs.

One of the most well-known and leading NoSQL database is MongoDB