How to Keep Unmatched Rows When You Join two Tables in SQL by Tihomir Babic 20 Jul 2021 Learn how to use JOIN to keep both matched and unmatched rows when you join two tables. Joining two or more tables is a skill you need a lot if you’re working with databases. And if you do it often, you’ve probably noticed not all data from one table corresponds to data from another table all the time. Sometimes, you need only the data that have a match in both tables. Read more The RANGE Clause in SQL Window Functions: 5 Practical Examples by Tihomir Babic 6 Jul 2021 What is a RANGE clause in SQL window functions? Five practical examples will show you how and when to use it. The RANGE clause is used quite rarely in SQL window functions. I don’t know why; maybe people are not used to it. This is a shame, because it’s far from a pointless clause; it can be very useful, and I’ll show you that in five examples. RANGE Clause Syntax When I’m talking about the RANGE clause, I’m talking about the one used in SQL window functions, which have the following syntax: Read more Business SQL: How to Calculate Revenue Growth in SQL by Tihomir Babic 16 Jun 2021 Can you use SQL in business? Of course you can! For example, you can calculate revenue growth in SQL – here’s how. As someone who works with data, you already know that SQL is the most used tool in data analysis. But how is SQL helpful in business use? Well, the answer is obvious: analyze business data using SQL! However, there are some specifics with business data that can be tricky if you’re not used to it. Read more Fun With SQL: How to Generate a Picture Using Recursive SQL Queries by Tihomir Babic 10 Jun 2021 Did you know that SQL can be used for fun? You can even ‘draw’ in SQL using recursive queries! Find out how in this article. As an SQL user, you already know this language is great for data analysis and data manipulation in general. This is something people get very serious about. But you can also have fun with it by drawing ASCII-art pictures using the SQL code. To do that, you have to know how recursive SQL queries work. Read more Top 10 SQL JOIN Articles for Beginners by Tihomir Babic 3 Jun 2021 Can’t find your way around the vast number of SQL JOIN articles? We’ve chosen ten JOIN articles that are worth beginning SQLers’ time. You probably know that there are many articles covering SQL JOINs. Some can be confusing because they assume pre-existing knowledge. Others are not written clearly and can leave even advanced users bewildered. The 10 SQL JOIN articles I’ve chosen are entirely the opposite. They’re written clearly and have some nice examples and visualizations. Read more 8 Best SQL Window Function Articles by Tihomir Babic 21 May 2021 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. Read more What Is Advanced SQL? by Tihomir Babic 19 May 2021 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. Read more Training SQL JOINs Doesn't Have To Be Difficult by Tihomir Babic 22 Apr 2021 How can you train your SQL JOIN skills? And where can you do this? Also, why should you even learn SQL JOINs in the first place? All of these questions will soon be answered. One of the positive sides of the internet era is information abundance. One of the negative sides of the internet era is, well, information abundance. The amount of information and knowledge available can be overwhelming. Read more Hierarchical Data and How to Query It in SQL by Tihomir Babic 20 Apr 2021 How do you recognize hierarchical data, and how do you query it? Two common SQL questions are about to be answered. Querying hierarchical data is a rather common situation if you’re working with SQL and relational databases. Not that hierarchical data is something mystical and rare; on the contrary, it’s everywhere. So why is hierarchical data so challenging when it comes to relational databases? Mainly, the difficulties occur in translating hierarchical data to relational database principles. Read more How to Find the Next Non-NULL Value in SQL by Tihomir Babic 6 Apr 2021 You need to find the next non-NULL value in a time series, but you don’t know how. Can you even do that in SQL? Yes, you can! This article will show you what to do. If you work with SQL, you will sooner or later confront NULL values. Having NULLs in a database is almost unavoidable. However, sometimes you want to avoid them in your reports. This is quite often true when you’re analyzing time series data; NULL values mean there’s no data available. Read more «« « 1 2 3 4 » »»