SQL Blog | LearnSQL.com

What is the Difference Between COUNT(*), COUNT(1), COUNT(column name), and COUNT(DISTINCT column name)?

by Tihomir Babic

29 Oct 2020 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.

What are SQL CTE Best Practices?

by Tihomir Babic

28 Oct 2020 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.

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

by Kateryna Koidan

27 Oct 2020 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.

Haunted Halloween Promotion - Join the Scavenger Hunt!

by Jakub Romanowski

25 Oct 2020 Trick or treat! Halloween, the festival of monsters is approaching! The LearnSQL platform is overrun by ghosts. They have haunted our courses. Are you scared, do you feel chills? We are most concerned about the prices. It’s highly probable the wraights will bite them off. But to quote the classics - “Who ya gonna call? Ghostbusters!” So put on the costume, take the astral trap and find them all to win our scavenger hunt.

How to Learn SQL Common Table Expressions (CTEs)

by Kateryna Koidan

23 Oct 2020 Common table expressions are very useful for organizing, traversing, and improving the readability of long SQL queries. Moreover, recursive CTEs, which can reference themselves, solve problems that cannot be addressed with other queries. But how do you master common table expressions in SQL? In this article, I discuss the most effective strategies for learning CTEs and suggest how to address the common challenges of learning common table expressions on your own.

What is a Primary Key in SQL?

by Ignacio L. Bisso

22 Oct 2020 Primary keys are an important concept in SQL databases. They provide a unique ID for every row in a database table. As an SQL developer, you should know what primary keys are, what data values are allowed in them, and how to create them. Read this article to learn the ABCs of primary keys in 10 minutes. How to Identify Rows in a Table Tables are the main objects in an SQL database, and as you probably know, tables store records or rows.

Learning SQL for Free – Is It Worth Betting on Free Online Learning?

by LearnSQL.com Team

21 Oct 2020 Everyone likes to get something for free, even when it comes to SQL courses. But is free always good? Find out how and where you can learn SQL for free – in a way that’s worth your time. Beginner-friendly database courses and SQL tutorials often promise to teach SQL fundamentals like SELECT, WHERE, GROUP BY, HAVING, and ORDER BY. These commands are the basis of a powerful set of skills for entry-level jobs in data analysis or databases.

What Is a DBMS?

by Adrian Więch

20 Oct 2020 We generate vast quantities every day, and that data needs to be stored somehow. That’s where DBMSs come in handy. Find out what they are and how they relate to databases. If you go on a diet and simply want to keep track of your weight, you can probably use a piece of paper and a pencil. If you then want to chart your daily caloric intake, you’ll probably switch to something like a computer spreadsheet.

Google Analytics and SQL

by Adrian Więch

16 Oct 2020 Google Analytics is a very popular tool among website and blog owners alike. With a simple and quick setup, it lets you gather data about your web page visitors easily. However, did you know that you can export data from Google Analytics to create your own SQL reports? Read this article to find out how. Google Analytics is an extremely popular and powerful solution that lets you collect and analyze various kinds of information about your website.

How to Boost Your Company With SQL Courses

by Rebecca McKeown

15 Oct 2020 SQL has the power to supercharge the capabilities and performance of your entire company. But if you don’t dip your toes in the water and give some SQL courses a go, you’ll never realize the vast potential of the language. SQL, or Structured Query Language, is your ticket to expanding the scope and the results of your business or organization, no matter what sector you operate in. Whether you’re the owner or manager of your company or simply an employee interested in improving operations, learning SQL is undoubtedly, unquestionably, for you.

1
2
3
29