Comparison of SQL Server with MongoDB As first sorry if I'm wrong with this here. For forwarding to the Right Place I'm grateful.  

To my issue: I'm in an internship as a programmer, no real experience with databases, and as I'm open-minded accepted to compare Microsoft SQL Server with MongoDB if there would be benefits for the company to change to it.

For the original data I've selected the kinda biggest 3 tables.  

Table: Article with over ~1,2 Mrd records

x-----------------------------x
| article_id|  suppID | ...   | 
x-----------|---------|-------x            
|    1      |     5   | ...   | 
|    2      |     6   | ...   |
|    3      |     7   | ...   |
x-----------------------------x


Table: Price with over ~2,3 Mrd records 

x-----------------------------x
| price_id  |ArticleID| ...   | 
x-----------|---------|-------x            
|    1      |     1   | ...   | 
|    2      |     2   | ...   |
|    3      |     3   | ...   |
x-----------------------------x


Table: Price_Archive with over ~5,8 Mrd records

x-----------------------------x
| article_id|  country| ...   | 
x-----------|---------|-------x            
|    1      |     DE  | ...   | 
|    2      |     EN  | ...   |
|    3      |     EN  | ...   |
x-----------------------------x


What are the main differences of SQL Server and NoSQL did I understand. But now more for the Technical Tests how can I achieve a comparison?  

As for migration I do a simple Copy Paste and use the $lookup for some test scenarios. Furthermore creating a main single collection (Articles) and integrate the other 2 Tables in it, as its wanted in MongoDB-Document-Oriented.  

Are there free tools where can log how much memory/time and so on is used for queries? Which other cases should I check?
SQL and NoSQL are different in many ways but the gist of it is that SQL is better at relational and NoSQL is better at non-relational. Each technology is suited for different purposes.

There are plenty of existing benchmarks and comparisons between the two such as here, here and here. Be wary of the bias in comparison articles and note that when someone says NoSQL is faster it could mean with less reliability.

To benchmark SQL queries you can look up the following:


SET STATISTICS TIME ON


Or use something similar to this:

DECLARE @DateTimeStamp DATETIME
SET @DateTimeStamp = current_timestamp
... --do some stuff to measure here
PRINT CAST(DATEDIFF(ms, @DateTimeStamp, current_timestamp) AS VARCHAR) + 'ms'


To benchmark MongoDB queries you can look up the following:


.explain("executionStats")
mongodb executionTimeMillis




Here are some comparisons between the two:

SQL


More expensive initial cost
Relational
Better data integrity with transactions ( more overhead )
More common so more developers have experience with it
More proven security
Paid tools for metrics and monitoring such as Solar Winds and Idera
There are likely free tools but I am not aware of them


NoSQL ( MongoDB )


Less expensive initial cost
Non-relational
No transactions ( less overhead )
Asynchronous INSERT and UPDATE
Depending on Write Concern Values it could be faster with less reliability or slower with more reliability
Possibly more scalable
Less proven security
Paid tools for MongoDB server metrics and monitoring such as Server Density.