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LEARNING ABOUT SQL - WITH SERGI LEHKYI

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LEARNING ABOUT SQL - WITH SERGI LEHKYI

Kelly Idehen

22nd Apr 2019

LEARNING ABOUT SQL - WITH SERGI LEHKYI

 SQL which stands for Standard Query Language  is a very important skill to learn in the computing world. Big Companies like banks & Telcos are constantly in search for people with this skill. 

By developing SQL skill, you can become a Business Analyst, a Developer, a DataBase Engineer & even become an Artificial Intelligence Specialist.

In this series we invited an expert from Barcelona to share with us on our FaceBook Group, on how you can get started with Learning SQL to becoming an SQL Professional. 

Follow the Chat series between Kelly Idehen and Sergi Lehkyi below.

#SQL_INTRO

LETS MEET Serhii Lehkyi Serhii Lehkyi, Data Scientist

My name is Sergi, I was born in Ukraine, spent 16 years in my hometown where I finished the school, after that I moved closer to the capital (Kyiv) to a town Irpin, where finished my bachelor degree in Economic Cybernetics with honor. At age 20 I moved to Barcelona to do my master in Business Administration and Marketing and since that time live in this beautiful city.

During the master I have already started to work with databases (I've got the basics during my bachelor degree) and was combining studies and work. Now I am the only data professional in our little telecom wholesale company where I manage all the data streams, reporting system and internal database, which didn't exist when I started in this company.

 

#SQL_Question_1

Kelly Idehen ; If you were asked to give the most simplistic layman (dummy) definition for SQL, how will you describe or explain it?

ANSWER:
Serhii Lehkyi : I will say it is the algorithm to find a book in a library.

 

#SQL_Question_2

Kelly Idehen : How is SQL different from MySQL, and SQLite? And what about NOSQL, all these names can be very confusing.. Can you throw a little light on these?

ANSWER

Serhii Lehkyi : SQL is a language - Structured Query Language to get desired data from relational database, like Python, R, C, C#, C++, Java, HTML, Go - whatever. MySQL, SQLite, PostgreSQL, MS SQL are RDBMSs - Relational Database Management Systems.

All of them use SQL, but each with their own little bit specific syntax. If you know base SQL you won't have difficulties in switching from MySQL to SQLite to Postgres and back.

NoSQL refers to Not only SQL and includes types of databases that are not relational and designed for high scalability and processing of large volumes of data.

To NoSQL family belong key-value databases (Redis, DynamoDB), document databases (MongoDB), graph databases (Neo4j, IBM Graph) and wide column stores (Cassandra, HBase).

The simplest differentiation between the two is the following: SQL - for structured, predictable data and NoSQL - for unstructured, unpredictable.

 

#SQL_Question_3

Kelly Idehen : How important is SQL to Machine Learning & AI practitioners and DataScientist?

ANSWER:

Serhii Lehkyi : Depends on how the organization stores the data. If the majority of data is in RDBMS and you have to query this data source on a daily basis - then it is very important.

Anyway, we still use and will be using structured data, so basics of SQL are necessary.

Do you need to know it on advanced level and be able to write mega complex queries - I doubt. For example, if you want to focus only on NLP (Natural Language Processing) I don't think you are going to deal with SQL. AI - the same situation, normally it doesn't use structured data, so no need for SQL.

In general I would rank these 3 fields in descending order of necessity of SQL like: Data Scientists, Machine Learning, AI.

 

#SQL_Question_4

Kelly Idehen : Have you ever done any AI related project that required SQL? How did it go?

ANSWER

Serhii Lehkyi : I haven't done a lot of AI related projects, but those I worked with (less than 10, and educational only) didn't require SQL.

 

#SQL_Question_5

Kelly Idehen : What would be your best advice for someone who wants to learn SQL?

ANSWER
Serhii Lehkyi : First, set up your mindset and start to believe that SQL is the easiest and most logical language - SELECT something FROM somewhere WHERE this condition meet - can it be clearer?

Second, think of a database as the library - if you were a librarian, how would you be looking for the book requested?

 

#SQL_Question_6

Kelly Idehen : Can you give a little background about your upcoming SQL course, why should we look forward to it…?

ANSWER

Serhii Lehkyi : I have worked with relational databases for almost 5 years and I have really mastered the query writing.

Triple joins that include self joins, grouping groups and selecting only top N (depends on request) values from that group of groups and other crazy stuff became normality for me.

And I have learned all this by articles and videos here and there, piece by piece until getting the complete picture inside of my head, which I would like to share with community and save their time learning some simple things that I realized only on 3rd or 4th year of work with databases (for example order of execution of SQL query).

Another goal is to create a course that will be more casual and fun, and not just another set of videos with the screencast and some monotone voice that explains you technical terminology.

 

#SQL_OUTRO

Kelly Idehen : Can you give us a little more detail about yourself and the work you do?

ANSWER

Serhii Lehkyi : My name is Sergi, I was born in Ukraine, spent 16 years in my hometown where I finished the school, after that I moved closer to the capital (Kyiv) to a town Irpin, where finished my bachelor degree in Economic Cybernetics with honor.

At age 20 I moved to Barcelona to do my master in Business Administration and Marketing and since that time live in this beautiful city.

During the master I have already started to work with databases (I've got the basics during my bachelor degree) and was combining studies and work.

Now I am the only data professional in our little telecom wholesale company where I manage all the data streams, reporting system and internal database, which didn't exist when I started in this company.

I still remember those days when I was importing and manually analyzing csv files with CDRs (Call Detail Records).

Those days we had 1 million calls passing through our network daily and today we reach 8-9 million thanks to my developments that helped to reduce to the minimum manual work of our sales people so they could focus on making new connections and contracts with better data background and valuable insights.

And now when I have enough confidence in my skills I decided to share it and contribute to the community through my blog, medium articles, course I am about to create and so on. It's just the beginning.

 

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