25 Jan 2022 Tihomir Babic The SQL OVER() Clause Explained Here is a detailed explanation of the OVER() clause in SQL window functions. This is a detailed guide on using the OVER() clause in SQL window functions. I will focus specifically on this clause, which requires that you have at least a general idea of how window functions work. To make the best out of this article, take a look at the SQL Window Functions Cheat Sheet. Feel free to have it by your side as we go. Read more 30 Dec 2021 Tihomir Babic How to Include Zero in a COUNT() Aggregate Explaining how to include zero (0) counts in your SQL query result. Here’s the problem: you want to count something that doesn’t exist, and you want to show your result as zero. How do you do that in SQL? Using the COUNT() aggregate function is a reasonable first step. It will count all the data it finds and return the number of occurrences. But what if there are no occurrences of certain data? Read more 9 Dec 2021 Tihomir Babic How to Join Tables in SQL Without Using JOINs Here’s how you can combine tables without the JOIN keyword. It seems like it shouldn’t be possible: join tables in SQL without using the JOIN keyword. But using the JOIN keyword is not the only way to join tables in SQL. This article will show you two additional methods for joining tables. Neither of them requires the JOIN keyword to work. They are: Using a comma between the table names in the FROM clause and specifying the joining condition in a WHERE Using UNION/UNION ALL. Read more 24 Nov 2021 Tihomir Babic Top 5 SQL CTE Interview Questions Here are five questions (and solutions!) on CTEs you’ll (probably) be asked at an interview. I’m not saying you will get these SQL CTE interview questions at every job interview. But when you do, they are probably along the lines of the five I’m about to show here. Other than theoretical questions about CTEs, there are not that many variations in the CTE scenarios evaluated by interviewers. Go through these five examples, and you get a good foundation for acing your interview! Read more 19 Oct 2021 Tihomir Babic What Is a Recursive CTE in SQL? The article that’ll show you practical examples of using recursive CTEs in SQL. If you’ve heard about SQL’s recursive CTEs but never used them, this article is for you. It’s also for you if you never get tired of recursive CTE examples. Before we dig into recursion, I’ll remind you what CTEs are and what their syntax is. Then I’ll do the same for recursive CTEs. After that, I’ll show you how recursive CTEs work in three examples. Read more 7 Oct 2021 Tihomir Babic How to Use CASE in ORDER BY in SQL This article will show you how and when to use CASE in an ORDER BY clause. Have you ever used a CASE statement? I’m sure you have, at least in a SELECT statement. But have you ever used it in an ORDER BY clause? No? You will, once I show you how! Don’t worry if you’ve never used a CASE statement. I’ll show and explain it to you with a short example. Read more 28 Sep 2021 Tihomir Babic Difference Between ROWS and RANGE in Window Functions Are you familiar with ROWS and RANGE window functions but not sure how they are different? This article makes those differences clear. In using SQL window functions, you’ve probably come across ROWS and RANGE clauses. If you haven’t, they are both parts of the Window Functions course. If you have, it’s quite likely you have been left confused why there are two keywords for the same function. Well, they are not the same! Read more 22 Sep 2021 Tihomir Babic The 7 Best Articles about the SQL Recursive Query Do you want to learn about recursive queries but don’t know where to start? Here’s our selection of seven articles that should help you with diving into the recursive queries world. I won’t lie to you. Learning and understanding recursive queries can be difficult. But difficult things are usually worth trying. And by learning recursive queries, you’re making sure you know how to work with this very powerful tool. Read more 10 Sep 2021 Tihomir Babic Frequently Asked Questions About SQL Ten SQL questions that you should be able to answer if you’re applying for an SQL job. SQL is a vast topic and a source of endless questions from its users. However, some questions are asked more frequently – usually about concepts that most SQL users will need to know. It’s not surprising that interviewers tend to ask these same questions to SQL job candidates. Either way, knowing these questions is a first step to learning SQL. Read more 26 Aug 2021 Tihomir Babic 3 Real-Life Business Questions That Are Perfect for SQL Common Table Expressions We answer three SQL business questions using CTEs. There are business problems that are often solved in a very roundabout way. While they might get you the correct result, there’s usually a more elegant way to write a solution. Enter the CTEs! They are extremely helpful when it comes to getting a more direct and elegant solution. I’ll show you three business situations where CTEs can be very helpful. You’ll get an idea of when CTEs can be useful. Read more «« « 1 2 3 … 5 » »»