How to Join the Same Table Twice by Marija Ilic 9 Oct 2020 JOIN is one of the most common statements in SQL. As you may know, it is used to join and combine data from two or more tables into one common data set. In this article, I’m going to discuss special types of joins? in which you combine the same table twice—including joining a table to itself, also known as the self join. When and why do you need to do this? Read more How to Create Your First Table in SQL by Marija Ilic 7 Oct 2020 Creating a database table with SQL is one of the core skills you’ll need to work with data. And it’s easy to learn, so let’s get started! Imagine you’re analyzing data and want to store your results in a database table. Sure, you've done this a million times in Excel. But you’re not sure how to create a table with SQL. Or maybe you’ve noticed that data engineering is in high demand and you want to start learning its core concepts. Read more What a Moving Average Is and How to Compute it in SQL by Marija Ilic 4 Sep 2020 Want to dive deep into time series data and examine long-term trends? Want to know what a moving average is and how to compute it in SQL? Then this article is for you. I’ll explain a powerful feature in SQL called window functions and show how you can calculate moving averages using them. What Is a Moving Average? The moving average is a time series technique for analyzing and determining trends in data. Read more How to Analyze a Time Series in SQL by Marija Ilic 23 Jul 2020 Values ordered by time are called a time series. In this article, I’ll show you the most frequent patterns and teach you how to write queries for time series in SQL with the help of window functions. Maybe you’ve had the opportunity to analyze some variables where each value was associated with a time value. Such data – where values are ordered by time – is called time series data. Read more What Is a CTE? by Marija Ilic 9 Jul 2020 After mastering statements like SELECT, DELETE, INSERT, and GROUP BY, you might search for ways to improve code maintainability, reproducibility, and readability. At that point, you will probably start learning about modern SQL concepts that were introduced in the early 2000s. One such SQL technique is the CTE? (common table expression) —?a temporary named result set. In this article, you will learn what a CTE is and how to use it to improve the maintenance and the readability of your code. Read more Why Should I Learn SQL Window Functions? by Marija Ilic 8 May 2020 SQL has been around for more than 25 years. Its basic syntax – like SELECT, WHERE, GROUP BY, HAVING, and ORDER BY – is well known. But is there something besides traditional SQL? Can you go beyond the basics and improve your skills? The answer to this question is yes. There is a modern version of SQL. In this article, we are going to dive into the modern version and learn about SQL window functions. Read more How to Analyze Time Series COVID-19 Data with SQL Window Functions by Marija Ilic 10 Apr 2020 The COVID-19 pandemic really changed the way we live. No matter where you are, you're being impacted by this unpredictable virus. We do not know what the future holds, but we do believe in science and in better days to come. One thing that makes me as a data analyst particularly happy is that we have publicly available data. We can analyze that data and learn something from it. If you want to explore COVID-19 with the help of modern SQL constructions, keep reading — this article is intended for you. Read more Should I Learn SQL as a Data Analyst? by Marija Ilic 4 Mar 2020 So, you are a data analyst—someone who relies on data. You like to gather, clean, and transform data and come to conclusions based on data. You are a data detective. Which tool do you choose to do your job in an elegant, reproducible, and simple way? Excel? R? Python? Or should you learn SQL? Stay tuned! In this article, I will explain why SQL is a must-have skill for data analysts. Read more How to Track Down Duplicate Values in a Table by Marija Ilic 4 Sep 2017 When it comes to information management, duplicates present one of the most common challenges to data quality. In this article, I'll explain how it is possible to find and distinguish duplicate names with the help of the SQL data programming language. I really like my maiden name. The reason I like it so much is because it's rare. My maiden name (first with last) provided a unique identifier on platforms such as LinkedIn, Facebook, Twitter and similar. Read more