Articles Cookbook
13 Nov 2020
Kamila Ostrowska

Practice SQL Before Interviewing a Potential Employee

Has your company grown to the point that you need to hire an SQL expert? Have you found a candidate for the job? How do you prepare for the interview, especially if you don’t know SQL? Don't worry! Follow our suggestions on how to practice SQL. We have tips and tricks to help you feel confident and find the perfect employee. Who You Want To Hire First of all, you need to know the requirements for the new employee.
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12 Nov 2020
Marija Ilic

SQL JOIN Types Explained

What’s the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN in SQL? When should you use each one? We’ve got your answers right here. You want to combine data from two or more different tables, but you’re not sure how to do it in SQL. There are different SQL JOIN types that you can use for different results. If you want to learn the differences between INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN, keep reading.
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11 Nov 2020
Zahin Rahman

Top 7 Online Courses for Data Engineers

This article summarizes the top online courses available for data engineers. We have picks suitable for beginners as well as intermediate learners. If you’re interested in database design and management, check these courses out! Most individuals who aspire to enter the realm of data aim for data scientist or data analyst roles. While these roles are indeed very rewarding because of their tangible links to customers and business direction, the role of data engineers is equally vital for businesses that operate in a data-rich environment.
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10 Nov 2020
Jakub Romanowski

SQL Terms Beginners Should Know

Have you started learning SQL? Do you feel a little lost in the maze of new words and ideas? Here’s a list of 10 absolutely essential SQL terms for beginners. When you start learning SQL, there’s a lot to process. And some of it – even basic SQL terms – gets lost in the shuffle. If this sounds like you, bookmark this article; it will be a handy reference.
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6 Nov 2020
Magdalena Wojtas

Where to Go After Learning SQL Basics

Learning to code is – in general – a lot of fun, for sure. Even after a few years in the IT industry, I still love learning new technologies. And I now know that learning with a good plan is even better than learning without one. This also applies to learning with advanced SQL courses. In this article, I'll show you how learning paths can save you some time and a lot of frustration.
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4 Nov 2020
Jakub Romanowski

Kickstart SQL Learning with Our SQL Basics Course

Why learn SQL from our interactive online courses? Two reasons: 1) Power up your career. 2) Avoid being a noob. What does it mean to be a noob? “Noob” comes to us from the world of computer games. It’s a combination of “newbie” and “beginner”. It’s not a very nice word. It means that someone has found you an inexperienced player and (even worse) resistant to learning. This resistance is what’s important.
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3 Nov 2020
LearnSQL.com Team

Course of the Month: GROUP BY Extensions in SQL

Do you want to develop your SQL skills? Do you want to get more out of your data and prepare better reports and summaries? The answer is learning to use SQL’s GROUP BY extensions. But how should you go about this? I asked the same question to Agnieszka Kozubek-Krycuń, Vertabelo’s Chief Content Officer. As she explains, the secret is in this November’s free SQL Course of the Month: GROUP BY Extensions in SQL.
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29 Oct 2020
Tihomir Babic

What is COUNT(*), COUNT(1), COUNT(column), and COUNT(DISTINCT) in SQL?

Have you noticed there are different variations of the SQL COUNT() function? This article explains the various arguments and their uses. As a SQL user, you’re probably quite familiar with the COUNT() function. Even though it’s relatively simple, it can be used in several different ways. Each way has a very different use. I imagine you’ve seen code that contains the function COUNT(*) or COUNT(1). You’ve probably also seen some other uses of the COUNT() function, such as COUNT(column name) and COUNT(DISTINCT column name), even if you haven’t used them.
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28 Oct 2020
Tihomir Babic

What are SQL CTE Best Practices?

Are you wondering what the best practices for using common table expressions are? This article will help you learn when to use a CTE and how to write it. If you have heard about SQL CTEs, you have probably noticed they’re often mentioned together with subqueries. Sometimes, people think there’s no difference compared to the subqueries, and there’s often debate about whether a CTE or subquery should be used to get a particular result.
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27 Oct 2020
Kateryna Koidan

How to Fix a 'Not a GROUP BY Expression' Error

Whether you are an experienced SQL user or only a beginner, your SQL queries may return errors. The accompanying messages are supposed to help you fix them; however, sometimes the messages are not very helpful. The Oracle message “Not a GROUP BY expression” is one such example. Let’s review what this is about and how to fix it. We are going to assume some basic understanding of how GROUP BY works.
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