23 Jun 2022 Tihomir Babic An Overview of Microsoft SQL Server Text Functions Data analysts use text values when creating SQL reports. You can create your own labels with functions, classify rows based on text value, or do computations based on it. This article covers how to do all that. The text values in databases are not just for reading. As with numeric values, we perform operations on them and manipulate the text. SQL Server has a fair number of text functions. Read more 7 Jun 2022 Tihomir Babic How to Combine Two Aggregate Functions in SQL Having trouble using two aggregate functions in one query? This article will show you how to do it the right way – actually, the two right ways. In data analysis and reporting, we often need to count the number of records or sum them up and then calculate the average of this count or sum. Translated to SQL logic, this is the aggregation of aggregated data, or multi-level aggregation. For aggregation purposes, there are the SQL aggregate functions. Read more 17 May 2022 Tihomir Babic Top 9 SQL GROUP BY Interview Questions Preparing for an SQL job interview? This guide will walk you through nine basic, intermediate, and advanced GROUP BY questions that you may have to answer. There are common GROUP BY questions that pop up in a lot of SQL job interviews; in this article, we’ll explain how to answer them. If you are a data analyst or another data professional preparing for an interview, this article aims to help you out. Read more 12 May 2022 Tihomir Babic What Are Window Functions in SQL? In this article, we discuss what window functions are and how they help you do your job as a data analyst or specialist. No, window functions have nothing to do with the operating system. The window here refers to a set of rows over which the function aggregates data. To learn how window functions work, what functions there are, and how to apply them to real-world problems, it’s best to take the Window Functions course. Read more 14 Apr 2022 Tihomir Babic The SQL OVER() Clause - When and Why to Use It The OVER() clause, or how to reach a whole new level of data analysis. Why all the commotion around the SQL OVER() clause? I’ll tell you why: the OVER() clause introduces window functions. And what are window functions in SQL, you might ask? They are functions that operate on a window, i.e. a set of rows related to the current row. In that way, they are similar to the GROUP BY clause and to aggregate functions. Read more 24 Mar 2022 Tihomir Babic How to Write Multiple CTEs in SQL Leverage the full potential of the CTE by combining two or more of them in a single SQL query. Common table expressions, or CTEs, can be a powerful SQL tool. When you write two (or even more) CTEs together, this power multiplies. In this article, I’ll show you three ways of writing multiple CTEs: Using two independent CTEs in one SQL query. Using two CTEs where the second CTE refers to the first. Read more 22 Mar 2022 Tihomir Babic The SQL Substring Function in 5 Examples Working with text data in SQL? We explain how to get values from any point in a string. When you think of working with data in SQL, your first thought is probably a database full of numbers and your SQL code doing very fancy calculations. But text is data, too! It’s very common to find text data in databases. Not only do you have to extract it, but often you also have to manipulate it. Read more 17 Feb 2022 Tihomir Babic How to Select the First Row of Each Group in SQL Grouping data in SQL is not that hard. Finding the first row of each group, maybe, but not after you read this article! You use GROUP BY when you need to group data in SQL. The GROUP BY statement groups rows with the same value into a single row. Due to its logic, it’s often used with aggregate functions. You know, functions like MIN(), MAX(), SUM(), COUNT(), AVG(), etc. Read more 10 Feb 2022 Tihomir Babic How to Query a Parent-Child Tree in SQL What are parent-child tree structures in SQL? In this article, we answer that question, talk about query hierarchy, and demonstrate the five most common SQL queries you’ll need for these data structures. Yes, you can use SQL on a parent-child tree structure. I’ll show you how in this article. Along the way, I’ll walk you through five query examples, starting with the easiest and ending with the most complex. Read more 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 «« « 1 2 3 … 6 » »»