13 Jun 2024 Gustavo du Mortier SQL CTEs: A Complete Overview of Common Table Expressions This article provides a detailed guide to everything you need to know about common table expressions (CTEs), from the basic definition to the most complex recursive queries. If the database you use supports CTEs, here’s everything you need to get the most out of it. Common table expressions – also called CTEs, WITH clauses, or recursive queries (although this last name is actually a specific application) – are a relatively new feature of SQL. Read more 14 May 2024 Gustavo du Mortier 11 SQL Common Table Expression Exercises In this article, we offer you 11 practice exercises that put your knowledge of common table expressions (CTEs) into practice. Each CTE exercise is accompanied by a solution and a detailed explanation. As the saying goes, “A little progress each day adds up to big results”. And that is undoubtedly true for SQL proficiency. Just as you should regularly go to the gym to keep your muscles toned, you should do common table expressions exercises often to keep your querying skills toned for heavy data analysis work. Read more 25 Apr 2024 Gustavo du Mortier 19 PostgreSQL Practice Exercises with Detailed Solutions You’ve probably heard the saying “practice makes perfect”. Find out if this phrase is true by trying the comprehensive set of PostgreSQL practice exercises that you will find in this article! To master any language, it is essential to practice it regularly so as not to lose the skill. This is as true for verbal communication as it is for programming. And SQL programming is no exception. Even the most seasoned PostgreSQL programmer needs to do PostgreSQL practice daily to perfect (and maintain) their skills. Read more 26 Mar 2024 Gustavo du Mortier How to Become a Big Data Engineer What is a Big Data engineer, and how is their skill set different from a data engineer? In this article, we explore the tools and platforms you’ll need to master as a Big Data engineer. To move from being a regular data engineer to a Big Data engineer, you need to acquire several new skills and learn to use several new tools. The good news is that Big Data still lets you use your good old SQL skills to manipulate and get information from data repositories. Read more 20 Feb 2024 Gustavo du Mortier MySQL Date Functions: Complete Analyst’s Guide Master MySQL date functions and acquire a powerful tool to work with date and time information in your data analyses. Working with date and time data is an essential part of data analysis. Here are just three examples: Analyzing historical time series data is crucial for discovering trends and making reliable forecasts based on chronological information. Stock market analysis examines time series data extensively, especially when automated trading algorithms are employed. Read more 30 May 2023 Gustavo du Mortier How to Use SUM() with GROUP BY: A Guide with 8 Examples Explore some real-world examples of using SUM() and GROUP BY in SQL, from the most basic to the most sophisticated. SUM() is a SQL aggregate function that computes the sum of the given values. GROUP BY is a SQL clause that partitions rows into groups and computes a stated aggregate function for each group. Using these two functions together, you can compute total sums for a group of rows. In this article, we’ll see 8 different examples of how you can combine SUM() and GROUP BY to create many different reports. Read more 26 Jan 2023 Gustavo du Mortier How to Group by Multiple Columns in SQL When analyzing large data sets, you often create groupings and apply aggregate functions to find totals or averages. In these cases, using the GROUP BY clause with multiple columns unfolds its full potential. GROUP BY is a clause of the SELECT command. It allows you to compute various statistics for a group of rows. For example, you can use GROUP BY with an employee table to know how many employees are of each gender. Read more 17 Mar 2021 Gustavo du Mortier What Is a NULL in SQL? SQL uses NULLs as a special flag that signals the lack of a value for a field or a variable. NULLs should be used wisely so the database gives a faithful picture of the reality it represents. Some people associate NULLs with zeros; others think that NULL means “none”. In SQL, neither of these are true. Simply put, an SQL NULL means that we don’t have a value for that particular field. Read more