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3 Sep 2020
LearnSQL.com Team
Fall 2020 Track of the Season: SQL from A to Z
During Fall 2020, our main SQL track, SQL from A to Z, will be in the spotlight. In this article, we answer the most frequently asked questions about this track. At LearnSQL.com, our SQL courses are organized into tracks. A track is a sequence of courses designed to help you achieve a specific learning goal. The courses in the track are in a recommended order that progresses from the easiest to the most challenging.
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2 Sep 2020
Zahin Rahman
How to Find Duplicate Values in SQL — The Ultimate Guide
Updated on: November 28th, 2023 Find duplicate values in SQL efficiently and avoid wasting resources. This article demonstrates how to locate and address duplicate records using SQL's GROUP BY and HAVING clauses. Database best practices usually dictate having unique constraints (such as the primary key) on a table to prevent the duplication of rows when data is extracted and consolidated. However, you may find yourself working on a dataset with duplicate rows.
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1 Sep 2020
LearnSQL.com Team
New Monthly Challenge for September 2020!
The new LearnSQL.com Monthly Challenge is ready! In September, we invite you to test your SQL skills to discover things about American movies, directors, and actors. Is this the first time you’ve come across our Monthly Challenge? LearnSQL.com delivers one Challenge per month, each a set of 5 to 10 SQL exercises prepared for those who want to practice their SQL skills. You won’t need more than an hour to solve these tasks.
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1 Sep 2020
LearnSQL.com Team
SQL Course of the Month – Analyzing Revenue Trends in SQL
We work hard, we learn SQL, and we develop professionally. But why? For our own satisfaction, but also for money! The knowledge of SQL will increase your income significantly. If you are proficient in SQL, you can better analyze your company's revenue. How? I asked Agnieszka Kozubek-Krycuń, Chief Content Officer at Vertabelo. In this article, she answers your questions about our September SQL Course of the Month: Analyzing Revenue Trends in SQL.
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28 Aug 2020
Adrian Więch
How CTEs Work
The SQL language offers a feature named Common Table Expressions, or CTEs. Also known as WITH clauses, CTEs are a fairly new addition to SQL. They help you break longer queries into smaller chunks, making your queries much easier to understand. Read the article to find out how to use CTEs and how they differ from traditional subqueries. Common Table Expressions (CTEs), which are essentially named subqueries, were first mentioned in the SQL standard between 1999 and 2000.
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27 Aug 2020
Ignacio L. Bisso
How Does SQL GROUP BY Work?
Grouping results is a powerful SQL feature that allows you to compute key statistics for a group of records. GROUP BY is one of SQL’s most powerful clauses. It allows you to see data in a new way and find key metrics (like the average, maximal, and minimal values in a group of records). Without GROUP BY, all the results we obtain are oriented to records. With GROUP BY, we can create groups of records and calculate metrics on each group.
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26 Aug 2020
Kateryna Koidan
SQL CTEs Explained with Examples
Learn how you can leverage the power of Common Table Expressions (CTEs) to improve the organization and readability of your SQL queries. The commonly used abbreviation CTE stands for Common Table Expression. To learn about SQL Common Table Expressions through practice, I recommend the interactive Recursive Queries course at LearnSQL.com. It contains over 100 hands-on exercises on simple and complex recursive CTEs. What does a CTE do? Why might you want to use one in your SQL code?
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25 Aug 2020
Tihomir Babic
How to Calculate the Length of a Series with SQL
What is a time series and why bother to calculate its length using SQL? How do we calculate the length of a series in SQL? I can answer that in two words: window functions! Yes, you’ll need some knowledge of SQL window functions to calculate series length. But what is a time series, and why would you want to find out how long it is? What Is a Series?
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21 Aug 2020
Jakub Romanowski
Where Can I Find Free Online Data Sets to Practice SQL?
Updated on 4th Sep 2023. Diving into the world of SQL can be an exciting journey. But to truly master this language, you need to practice SQL regularly. In this article, we'll guide you through some free online data sets that will help you take your SQL practice to the next level. Let's get started! You've successfully installed your chosen RDBMS and grasped the basics of SQL. So, what's the next step?
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20 Aug 2020
Adrian Więch
5 Examples of GROUP BY
When you start learning SQL, you quickly come across the GROUP BY clause. Data grouping—or data aggregation—is an important concept in the world of databases. In this article, we’ll demonstrate how you can use the GROUP BY clause in practice. We’ve gathered five GROUP BY examples, from easier to more complex ones so you can see data grouping in a real-life scenario. As a bonus, you’ll also learn a bit about aggregate functions and the HAVING clause.
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