Articles Cookbook
28 Mar 2023
Tihomir Babic

How to Solve the “must appear in the GROUP BY clause or be used in an aggregate function” Error in PostgreSQL

Learn what causes one of the most common PostgreSQL GROUP BY errors and how you can fix it! As a PostgreSQL user, you surely encounter many error messages when writing an SQL code. Sometimes they are quite unclear, but you won’t need an interpreter for this one: “must appear in the GROUP BY clause or be used in an aggregate function”. This error message mentions GROUP BY and aggregate functions.
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23 Mar 2023
Jill Thornhill

How to Practice Advanced SQL Online with LearnSQL.com

Want to go from intermediate to advanced SQL user? You’ll need to practice! Here are some ways you can practice advanced SQL online. You’ve seen how SQL helps you make data-driven decisions. Perhaps you’ve even learned some advanced features. But you’d like to become an expert—and for that, you need practice, practice, and more practice. Is it possible to get advanced SQL practice online? Taking SQL to the Next Level What is advanced SQL?
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21 Mar 2023
Kamila Ostrowska

Best MySQL Courses for Beginners

SQL is among the most important languages when it comes to dealing with huge amounts of data. If your job includes analyzing or collecting data and you feel that an Excel file is not enough, you need to learn or develop your SQL skills. And if you learn SQL, you also need to know one of its most popular dialects - MySQL. If you've made the decision to learn SQL, you've come to the right place.
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16 Mar 2023
Tihomir Babic

The SQL COUNT() Function: A Detailed Guide

This guide will give you a detailed explanation (with examples) of all the typical uses of the COUNT() function. Exercises included! The COUNT() function in SQL is one of the most commonly used aggregate functions. Aggregate functions in SQL are used to calculate statistics for a group of rows: counting the number of rows in each group, computing the sum of values in a group, finding the minimum or maximum value in a group, and so on.
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14 Mar 2023
Jakub Romanowski

Learning SQL in Your Native Language is Finally Possible

Do you or someone you know speak English as a second language? Would you like to learn SQL online in your preferred language? Good news! Our awesome SQL courses are now available in French, Spanish, German, Italian, and Portuguese! SQL, or Structured Query Language, is a programming language used for managing and manipulating data in databases. It's an essential skill for anyone working with data, whether you're a data analyst, a software developer, or just someone who wants to understand how databases work.
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9 Mar 2023
Maria Durkin

The Best Apps to Learn SQL

Let us guide you to the best apps for learning SQL on the go. They are designed to seamlessly integrate into your busy lifestyle – ensuring you develop your database skills anytime, anywhere. Are you eager to dive into SQL but unsure where to start? This article is your ultimate guide to the top apps for learning SQL. We include suggestions tailored for users of all levels, from beginners to advanced learners.
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7 Mar 2023
Jill Thornhill

The Best YouTube Channels for Learning SQL

Discovering the best YouTube channel from which to learn SQL is essential for beginners and enthusiasts alike, as SQL learning doesn't have to be challenging. If you're wondering whether watching online videos is the most effective way to master SQL, it's crucial to explore and identify high-quality YouTube channels dedicated to teaching SQL. This approach ensures you gain a comprehensive understanding of SQL through engaging and informative content. So you’re thinking of learning SQL?
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28 Feb 2023
Ignacio L. Bisso

25 Advanced SQL Query Examples

One of the best ways to learn advanced SQL is by studying example queries. In this article, we'll show 25 examples of advanced SQL queries from medium to high complexity. You can use them to refresh your knowledge of advanced SQL or to review before a SQL interview. Table Employee Many of the examples in this article will be based on the following employee table. Only a few examples will be based on other tables; in these cases, the tables will be explained along with the example.
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23 Feb 2023
Tihomir Babic

Top 27 Advanced SQL Interview Questions with Answers

Where can an SQL professional find a comprehensive guide to advanced SQL interview questions? The shortest answer is: here! We selected the 27 most important SQL questions and answered them for you.  Preparing for an SQL interview is not easy, especially if your job requires the knowledge of advanced SQL. This article contains the 27 most commonly asked advanced SQL interview questions and provides detailed answers and resources for further reading.
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21 Feb 2023
Tihomir Babic

6 Useful Examples of CTEs in SQL Server

How can you use CTEs in SQL Server in your everyday professional life as a data pro? We’ll answer this question by giving you six examples. CTE is short for Common Table Expression. This is a relatively new feature in SQL Server that was made available with SQL Server 2005. A CTE is a temporary named result. This result is available only for the query that runs it. It isn’t stored, so it doesn't take up disk space.
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