25 Jul 2023 Tihomir Babic Using GROUP BY and ORDER BY Together: A Guide Untangling how to use two basic SQL clauses – GROUP BY and ORDER BY – in one query. GROUP BY and ORDER BY are basic SQL clauses. As such, they are taught relatively early in the learning process. And they usually don’t present a big hurdle to beginners. However, using GROUP BY and ORDER BY together can be confusing. By the end of this article, your confusion on this subject will go away. Read more 20 Jul 2023 Tihomir Babic A Complete Guide to Working With Substrings in SQL In this article, we’ll discuss how to work with substrings in SQL. It involves learning several approaches, so we’ll show you their ins and outs. To work with substrings in SQL, we first need to know what a string is. In programming, a string is any kind of textual data (a title, a description, a name). A string consists of any number and type of characters. In a SQL database, strings are typically stored as CHAR or VARCHAR data types. Read more 20 Jun 2023 Tihomir Babic What Is a LEFT OUTER JOIN in SQL? 4 Practical Examples Today’s article will discuss the LEFT OUTER JOIN in SQL. We’ll go through several examples of LEFT OUTER JOIN usage and compare it with INNER JOIN. A JOIN is an SQL feature that allows you to combine data from two or more tables. The nature of relational databases makes JOIN one of the most commonly used features in SQL. Why? In practice, you’ll very seldom have all the required data in one table. Read more 27 Apr 2023 Tihomir Babic How to Use the SQL RANK OVER (PARTITION BY) Ranking data in SQL is a breeze if you know how to use RANK() to rank over a partition. This article shows you how to do it, as well as how RANK() differs from DENSE_RANK() and ROW_NUMBER(). If you work with SQL in a professional setting, you have had to rank data at least once. Think of ranking months/years/quarters by revenue or costs, best-selling products, most viewed posts or streamed songs, employees by salary, most profitable branches, you name it. Read more 18 Apr 2023 Tihomir Babic 10 Beginner SQL Practice Exercises With Solutions Solve these ten SQL practice problems and test where you stand with your SQL knowledge! This article is all about SQL practice. It’s the best way to learn SQL. We show you ten SQL practice exercises where you need to apply essential SQL concepts. If you’re an SQL rookie, no need to worry – these examples are for beginners. Use them as a practice or a way to learn new SQL concepts. Read more 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. Read more 16 Mar 2023 Tihomir Babic The SQL COUNT() Function: A Detailed Guide Updated on: April 22, 2024 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. Read more 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. Read more 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. Read more 19 Jan 2023 Tihomir Babic What Is a CTE in SQL Server? What is a CTE, and how do you write a CTE in SQL Server? Join us on a journey where we’ll see all the typical usage of a CTE in SQL Server. CTEs (or Common Table Expressions) are an SQL feature used for defining a temporary named result. You can think of it as a temporary table whose output is available only when the main query is run. This is practical because the CTEs result isn’t stored anywhere but can always be referenced inside the query like any other table. Read more «« « 1 2 3 … 8 » »»