Introduction to MongoDB

Hello everyone. After a long time, again I am starting a new part of my blogs.
This part will involve about getting started with MongoDB in C# for the
beginners. This will include basic introduction to NoSQL, MongoDB, a C#
console application and Azure CosmosDB. Don't wanna bore you with just
infos. So let's get started.

First of all, what is NoSQL? NoSQL (originally referring to "non SQL",
"non relational" or "not only SQL") is a query language which uses a different
mechanism of storage and retrieval of data in non-relational databases,
unlike the tabular relations used in relational databases. NoSQL stores data
in a key-value pair. A simplest example of NoSQL would be like :
{ "FirstName" : "Alex", "Age" : 25, "Email" : "alex@gmail.com" }
Wait a second! This example rings a bell, isn't it? It looks just like
JSON data. You are absolutely right. Most of the non-relational databases
use JSON as their preferred input/output format. If you don't have the
knowledge of JSON, no worries. Just study a little bit about JSON and you
will be ready to go.

Next is the platform where these NoSQL statements will be executed.
Like SQL statements are executed in the relational databases like
Microsoft SQL Server, Oracle, MySQL, etc. Similarly, NoSQL statements
are executed in non-relational databases like MongoDB, RavenDB,
CouchDB, DocumentDB, etc. In our blog, we will be focusing on MongoDB.
Before getting started with MongoDB, you might wanna know when and
where to use NoSQL. Although, this question is quite debatable.
Still, you can refer to Ted Neward's Blog which will clear out
some mist.

MongoDB (from humongous) is a free and open source database,
published under the GNU Affero General Public License which
stores data in a document-oriented format. MongoDB uses
JSON-like documents with schemas. It stores the data in the
BSON (Binary JSON) form in the database. But uses JSON as
preferred input/output format.

As mentioned earlier, MongoDB is free and open source software
which can be easily downloaded from the official website.
Just download the Community Server edition MSI installer
for Windows and install.

Once installed, you need to verify whether everything works
fine or not. By default, MongoDB wants to store data in the
default file system path, C:\data\db, but this is configurable
with a text file passed by name on the command line via --config.
Again by default, C:\data\db directory won't exist and
installing MongoDB won't create this directory. You have to
manually create this directory or configure the system path to
your preferred directory. If you don't do it, the MongoDB server
won't work properly. Let's not get into the hassle with
configurable system path and keep it simple with the
default system path.

Now open up command prompt by pressing Windows + R keys and type
cmd and press Enter. Navigate to the directory
"C:\Program Files\MongoDB\Server\3.4\bin" by executing these
commands :

cd ..\..
cd "C:\Program Files\MongoDB\Server\3.4\bin"

If you navigate to this directory in terms of folder view,
you will notice a bunch of files out of which you need only
two executable files to get you started - mongod.exe and
mongo.exe.

The mongod.exe is the database process itself and the
mongo.exe is the command-line client for executing
NoSQL statements.

Now in the command prompt, type "mongod.exe" and press Enter.

If the the text "waiting for connections on port 27017"
comes up, you will know the MongoDB server is up and running.
Minimize this command prompt window and open up another
command prompt window. Navigate to the same directory
"C:\Program Files\MongoDB\Server\3.4\bin" and fire up "mongo.exe".

This is the client for executing NoSQL commands.

So, let's start writing few commands for better understanding.

1. db.adminCommand( { listDatabases: 1 } )
This command displays the list of databases in MongoDB Server.
The default database is "test".

2. db.getCollectionNames()
This command displays the list of collection in the current database.
The default collection is "things".

Here, you can think of collection as table.

These are more database related commands. For further details,
you can refer to this link.

3. p1 = {"PersonFirstName":"Alex","PersonAge":28}
    db.things.save(p1)
The first command creates a temporary document p1 which contains
the actual data to be stored in the collection "things".
Here, document is not a file, like word(.docx) file,
text(.txt) file, etc. Rather it refers to the row/tuple
that contains the data. The keys ("PersonFirstName" or "PersonAge")
in it are known as elements of the document.
The second command actually stores p1 temporary document in the
collection "things" permanently.

4. db.things.find()
This command displays the list of documents in the
collection "things" (a maximum count of 20 documents).

Here, you notice that there is another element "_id" that
you didn't create. It is auto-generated for uniquely
identifying the document. You can think of it as
"Primary Key".

5. findP = {"PersonFirstName":"Alex"}
    db.things.find(findP)
This command displays the specific document with the passed
parameters.

6. testP = {"PersonAge":28}
    setP = {"PersonFirstName":"Brandt"}
    db.things.updateOne(testp,{ $set : setp })
This command updates the element "PersonFirstName" from "Alex"
to "Brandt" of the specific document with the "PersonAge" as 28.

7. db.things.deleteOne(testP)
This command deletes the specific document.

These are the basic CRUD operation commands. For more details,
you can refer to this link.

Now to close the mongo.exe client, type "exit" and press Enter.
Close this window.
Again to close mongod.exe process, press Ctrl + C.

That's all.  I hope this blog helps you to get started with MongoDB.
Till then, stay tuned. Keep Coding!!!