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Articles
Cookbook
26 May 2021
Ignacio L. Bisso
How to Compute Year-Over-Year Differences in SQL
How did your business do this year compared to last year? The year before? Find out how to use SQL to calculate year to year and month to month differences. Year-over-year (YOY) comparisons are a popular and effective way to evaluate the performance of several kinds of organizations. Year to year differences are easy to understand – e.g. it’s easy to understand that your revenue growth is 35% year to year.
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25 May 2021
Karolina Niewiarowska
How to Keep Focused While Learning SQL
Updated: April 29, 2024 Learning SQL can be a challenge, but it’s one you can handle! I’ve prepared 5 tips to help you stay focused during your learning journey. By choosing the right methods and tricks, you can achieve your goals! If you’re interested in learning SQL, I bet that you are a very ambitious person who wants to constantly develop. You may even be taking your first steps in your career.
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21 May 2021
Tihomir Babic
8 Best SQL Window Function Articles
Do you need a starting point for learning SQL window functions? Not sure which articles provide a solid foundation? We dove into the internet rabbit hole and found the eight best articles dealing with window and analytic functions. There are plenty of articles dealing with SQL window functions. Type those words into Google and you’ll find a huge number of articles returned. Reading articles is a good start if you want to learn something about window or analytic functions in SQL – provided, of course, that the articles you choose are trustworthy and up to date.
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20 May 2021
Martyna Sławińska
What’s the Difference Between UNIQUE and DISTINCT in SQL?
We use the words unique and distinct interchangeably in our day-to-day life. However, these words play very different roles in SQL. Let’s find out what is so different about them and how we can use them in SQL. Despite the words unique and distinct being synonyms, they cover very different things in SQL. The UNIQUE keyword in SQL plays the role of a database constraint; it ensures there are no duplicate values stored in a particular column or a set of columns.
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19 May 2021
Tihomir Babic
What Is Advanced SQL?
Are you confused about advanced SQL skills? What are they? This article will explain what advanced SQL can mean, especially as we use it on LearnSQL.com. I’m sure you find the phrases ‘advanced SQL skills’ or ‘advanced SQL topics’ very often. You read one article about advanced SQL and you’re happy with how easy these advanced topics seem to be. Then you talk to someone and you see they consider everything you know as basic SQL knowledge.
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18 May 2021
Andrew Bone
How to Use Aliases in SQL Queries
An SQL alias is useful for simplifying your queries and making the query and its result more readable. This article explains why and how you can use aliases in your SQL queries. You can temporarily rename a table or a column by giving it another name. This is known as an SQL alias. It’s a temporary change that does not affect the actual table name in the database. A temporary table name can also be called a correlation name.
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14 May 2021
James Wondrasek
How to Use Comparison Operators with NULLs in SQL
The SQL NULL value serves a special purpose. It also comes with counterintuitive behaviors that can trip up SQL beginners or even experienced programmers. Learn how to avoid these problems when you use NULL with comparison operators. This article is going to help you master best practices for crafting SQL queries that work with NULL values and use comparison operators ( =, <>, <, > ) – which, if you have written any SQL queries before, you know is just about every query you will ever write!
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13 May 2021
Kateryna Koidan
A Detailed Guide to SQL ORDER BY
It’s often necessary to display the output of SQL query in specific order rather than arbitrarily. In this article, I’ll explain the many ways you can do it with the SQL ORDER BY clause. To sort records in SQL, you’ll need to use the ORDER BY clause. In this article, I’ll explain in detail how to use ORDER BY to sort output by one or more columns, in ascending (A-Z) or descending (Z-A) order, and by using existing column(s) or using column(s) calculated by an aggregate function.
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12 May 2021
Kamila Ostrowska
The Best Books for Data Engineers
Are you tired of staring at a computer all day? Maybe it’s time to read a book. Take a moment to check out our list of recommended books for data engineers. They will help you deepen your knowledge about databases. Last year, we shared a list of the best books to learn SQL. This time, I want to introduce five books for data engineers. They are worth reading and will help you learn more about databases.
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11 May 2021
Karolina Niewiarowska
Best Online SQL Courses for 2021
In this pandemic era, it's no surprise that online learning has become even more popular. To help you narrow things down, I’ve prepared a list of 2021’s 10 best online SQL courses. Find out where you can learn SQL effectively! The number of online courses on offer – especially in the tech industry – is now impressive. You can find something that suits your interests, competences, and professional ambitions. But how do you know which to choose among the many online SQL courses out there?
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