Introduction to Databases - SQL, NoSQL, Graph Databases, Blockchain

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Well explained Ivan.


I’m still a little unclear with Graph databases. I sort of get what it does, but I guess I might like to see the ‘how’ it gets it. Perhaps it would have been helpful to see real-time querying of a SQL database, a NoSQL database and a Graph database. I’m looking forward to your discussion on how private blockchains brings them all together.

I agree it would be useful to see this in practice. Although I have no idea how easily “accessible” it’d be for Ivan to get access to different databases. I’m sure there’d also be some funky security/privacy issues there.

This video shows some examples of Graph databases and takes more of a deep-dive on it:

For SQL and NoSQL database examples:

Hope these help :slight_smile:


Good explanation about SQL, NoSQL ans Graph databases!

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Ivan is an amazing teacher, it is incredibly how such a young adult can explain complex things in a way that everyone can understand. Thanks so much for this excellent course packed with knowledge.

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I have a general question about which database to choose for a project.
Imagine, I have several sensor with data (timestamp and a value). That means I would choose NoSQL because I only have key-value pairs. But what if these data of the sensors have a clearly relationship to each other? For example I have a sensor which measure the pressure, the force, the displacements, the the vibrations and so on and so forth. And we know that the data of the sensors have a relationship together (pressure increase, force increase, vibration increase etc.). Which one should I use now? SQL? NoSQL? Or Graph?

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Good question, I see you posted this a couple of days ago.

I’m intrigued. Could you please post what you found out? I would be interested to know… :thinking:Ivo

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I would like to give you an answer, but I cannot. I thought the community here is more active…

I don’t understand. what does that have to do with the community being active? Did you even try to do a google search? and you found nothing at all? If even google don’t know, how would we know? I don’t get it.:thinking: maybe it’s because of the language.

Did you really mean that you wanted us to do the google searching for you, read the answers, then come back to this post, and explain to you what we found? is this a joke?


Please, Do us all a favor and at least try to find the answer yourself. Don’t always rely on others to hand you the answers on a sliver plate. You are taking the business masterclass, and I’m shocked that you waited 2 days for something that took under 10 seconds to find the answer to. To me, this is pure laziness. just being honest!

Here are your answers.

You can read it yourself, and see if you are able to make a decision on what fits your own project.


Hello Ivo,

I have to say your answer is very unfriendly and not professional. Of course I googled it but I did not found a clear answer. OK, I google maybe 5 minutes, but not more, don´t wanted to waste a lot of time, because it was just a theoretical question. I thought it would be nice to post such question so that other people who has the same question can read also the answer. I wanted an answer from someone who has real experience with such an issue (implemented such a thing in real and not in writing just the theory in google). That being said I don’t wan´t someone to google something for me, I am able to do so. Of course, I can make a decision what the best is, but I as I said before I wanted to have an answer from someone who has implemented such issue in real practical applications. Next time I will add something to my post that it would be nice to have an answer from someone who has practical expertise on it.
And Ivo, call someone you don´t know in person over the internet lazy is shocking to me. Especially when you are working for a company and represent it on the internet. Why should I use the academy when it is not welcome to ask questions or get such answers?

However, thank your for your time and answer.

  1. Row = a single record or dataset in a table
  2. Column = a field or attribute in a record
  3. Table = a set of records that have similar attributes
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Very clearly explained. SQL NoSQL, GRAPH Publick Blockchain Private Blockchains All very interesting and looking forward to further videos. D

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Thank you for your inputs. I appreciate them and take them to heart.


Hi, I am struggling to define the purpose of a graph database in my notes from the video explanation, would you say that with the restaurant analogyexplanation I could simple say that graph databases are used for more complex relations (which is said in the video) such as relations that involve ‘a greater number of variables’? or if not variables perhaps conditions. I feel as though that was what was being got at in the video?

That was good. I wasn’t previously aware of Graph DBs

Another example of a situation a graph database fits best is a chamber of commerce organization. They are storing all information from company’s and their shareholders. You can be shareholder in many company’s to get a clear overview of all company’s a shareholder can be involved fits best to a graph database.

I always used sql for everything but after this video I realized that
database graph also does the same as the other databases so it’s the best for everything,and faster than sql.

As I am new to the more technical parts, this was quite enlightening. Still not sure I understand Graph databases … but let’s see, maybe more to come…

I guessed that most of questions should be about Graph Databases. I have never used them, but @ivan’s example allowed me to craft my own one.

Let’s suppose that Joaquín tested positive for COVID. In my country, you should be asked to name every person that was in direct contact with him during the last week or so, in order to run a PCR test over them. You can see that this may have a cascade effect, as if one of them tests positive, you will need to get the list of their direct contacts and so (it is a recursive definition). SQL databases are bad at answering recursive queries over relationships where you don’t know beforehand how many levels does the cascade has.

In this example, a relational database would be great to answer the query “who was in direct contact with Joaquín during the last week”. However, if you would want to follow the traceability of this case (say, find every person that might got COVID because Joaquín got it, which means that you are following this cascade effect), you will struggle a lot using SQL, because you would need to run multiple queries to find that result, at least one for each degree of separation (say, if Joaquín passed the virus to Catalina, Emilia and Pilar, you should check if they have passed the virus to someone else, and you will continue doing it as much times as you need until you have no results. As we said before, this is a bad case scenario for SQL)
I imagine that a Graph Database may answer to this question with only one query, in a much easier way.