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Articles
Cookbook
28 Jan 2021
Andrew Bone
Using AND, OR, and NOT Operators in SQL
AND, OR, and NOT are important logical operators in SQL. They help you combine the conditions used to filter records. They are most commonly used in conjunction with the WHERE or HAVING clauses. Furthermore, this topic is a pretty common SQL job interview question. To help you completely understand these operators, I’ll take you through some examples, fully explaining the syntax and purpose of each. Practicing using examples like these is one of the best methods for learning SQL.
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27 Jan 2021
Agnieszka Kozubek-Krycuń
Why Aren’t SQL Window Functions Allowed in GROUP BY?
It’s true – the SQL order of operations means window functions aren’t allowed in GROUP BY. But you can use them anyway with this special trick. SQL window functions are one of the language’s most powerful features. However, the syntax of window functions is not easy to master. It has lots of details that can cause beginners to stumble. One of the most common traps is trying to use window functions in GROUP BY.
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26 Jan 2021
Marija Ilic
7 Common GROUP BY Errors
Are you making these errors with GROUP BY in SQL? Find out what they are, how to avoid them, and how to fix them. SQL’s GROUP BY statement can quickly uncover powerful data insights. At first, using GROUP BY can seem easy – e.g. when creating basic SQL reports that you’ll present to business decision-makers. But while learning this powerful feature, you could become trapped in weird errors or get incorrect results caused by improperly written GROUP BY statements.
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26 Jan 2021
LearnSQL.com Team
SQL Puzzle Day 2021
Do you like fun? This Friday, January 29 is National Puzzle Day, the perfect day to do a little brain exercise. We have prepared something special for you to mark this occasion. Join in with the game and get a big discount. The rules are simple. You have to put together a tough and fun jigsaw puzzle. We have hidden a promo code somewhere in the picture. Enter this code when purchasing our All Forever SQL Plan and you will get a $220 discount.
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22 Jan 2021
Zahin Rahman
Why Learn SQL Window Functions in 2021?
SQL window functions provide some extremely powerful and convenient features for data practitioners. This article explains why you should learn window functions and when you should use them. I’ll also provide some examples to help you visualize the concepts. Window functions are part of advanced modern SQL – knowledge of which will definitely enrich the repertoire of any SQL user. Window functions have a broad range of uses and can be applied to almost all facets of business.
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21 Jan 2021
Zahin Rahman
Where Can I Find Good SQL CTE Exercises?
Find the top online resources for SQL Common Table Expression (CTE) exercises! CTEs allow you to structure and organize SQL queries efficiently, which is essential if you want to advance your SQL knowledge. A Common Table Expression, or CTE, is a SQL syntax that creates a temporary data set. This set contains separate data than the main query, which can typically be referenced or reused in a subsequent query. A CTE is considered temporary because the result is not permanently stored anywhere and only exists for the duration of the query.
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20 Jan 2021
Jakub Romanowski
Stories of the LearnSQL Scholarship Program
2020 is behind us. It was an extremely difficult year: We’ve struggled with the Covid-19 pandemic, a worldwide economic crisis, and constant anxiety. Many people have lost their jobs and their prospects for a better tomorrow. That's why we decided to do something positive: establishing a SQL scholarship program. We decided to find people in difficult situations and try to help them. For many, learning SQL can be their chance to get a job and develop their career.
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19 Jan 2021
Andrew Bone
What Is the SQL WHERE Clause?
The WHERE clause is a fundamental part of SQL. This clause filters results and applies conditions to SQL queries. It is most commonly used alongside the SELECT statement. If you’re a complete newcomer to this topic, you can learn the basics of SQL, including WHERE, in our SQL Basics course This article will clearly explain how to use WHERE in a SQL query. After reading it, you’ll have the confidence and knowledge to integrate WHERE into your daily work.
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14 Jan 2021
Agnieszka Kozubek-Krycuń
Monthly SQL Challenges in 2021
Did you know that LearnSQL.com provides a monthly SQL Challenge? Every month, we publish a new set of SQL practice exercises. Find out what to expect from our SQL challenges in 2021. Here at LearnSQL.com, we believe that the best way to learn SQL is through practice. After all, writing SQL is a practical skill. That’s why all our SQL courses (and there are over 30 of them!) are interactive: You learn SQL by writing SQL code.
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14 Jan 2021
Kateryna Koidan
What’s the Difference Between SQL CTEs and Views?
SQL views vs. CTEs: What do they do? How are they different? Which one should you use and when? Get your answers here! In SQL, both CTEs (common table expressions) and views help organize your queries, leading to cleaner and easier-to-follow code. However, there are some important differences between them. This article will walk you through several examples of CTEs and views and explain when to use each one.
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