Group By

Tihomir Babic

GROUP BY and Aggregate Functions: A Complete Overview

SQL’s GROUP BY and aggregate functions are essential in data aggregation – and for analyzing data and creating reports. Let’s explore them together!   In SQL, GROUP BY and aggregate functions are one of the language’s most popular features. Data aggregation is critical for data analysis and reporting; to make sense of all the data in a dataset, it often needs to be aggregated. But what is data aggregation? Put simply, it’s when you group data based on common values and perform a calculation for each data group.

Maria Durkin

SQL HAVING Clause: A Tutorial for Beginners

So, you're new to SQL and have just stumbled upon the HAVING clause. But what does it do? Why is it essential? In this article, we'll delve into the basics of the HAVING clause in SQL. And we’ll walk through practical exercises to enhance your understanding of its functionality. Let's start by defining Structured Query Language (SQL). SQL is a powerful and standardized programming language designed specifically for managing and manipulating relational databases; simply put, it is how we communicate with the databases that hold all of our important data.

Maria Durkin

SQL Aggregate Functions: A Comprehensive Guide for Beginners

Are you curious about SQL aggregate functions and how they apply to real-world scenarios? In this article, we'll explore SQL aggregate functions, showcase real-world examples, and offer valuable insights on how to master them. Data aggregation is the process of taking several rows of data and condensing them into a single result or summary. When dealing with large datasets, this is invaluable because it allows you to extract relevant insights without having to scrutinize each individual data point.

Ignacio L. Bisso

10 GROUP BY SQL Practice Exercises with Solutions

Need to practice your SQL skills? These 10 GROUP BY practice exercises – with explanations and solutions – are a great start! GROUP BY is a powerful SQL clause that allows you to create groups of records and then calculate summary metrics (such as averages) for those groups. However, GROUP BY is often challenging for SQL learners to master. Yet, practicing GROUP BY is very important if you’re planning on using SQL.

Dominika Florczykowska

What Does GROUP BY 1 and GROUP BY 1, 2, 3 Mean in SQL?

Have you ever come across the unfamiliar GROUP BY 1 syntax in SQL queries and wondered what it's all about? Well, you're not alone! In this article, we'll dive into this syntax, explain its purpose, and make it easier to understand. Whether you are a regular SQL user or you’re just beginning to learn this language, you have probably worked with GROUP BY before. The GROUP BY clause in SQL is used to group rows from a table based on one or more columns.

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.

Radu Gheorghiu

How to Use COUNT() with GROUP BY: 5 Practical Examples

Using the COUNT() function with GROUP BY is one of the most common SQL constructs in aggregate queries. Read this article to find out how to use COUNT() with GROUP BY correctly using 5 examples. In this article, we will explain the importance of using COUNT with GROUP BY. We’ll talk about why it is essential in SQL and how it enables data analysis and summarization based on specific criteria.

Gustavo du Mortier

How to Use SUM() with GROUP BY: A Guide with 8 Examples

Explore some real-world examples of using SUM() and GROUP BY in SQL, from the most basic to the most sophisticated. SUM() is a SQL aggregate function that computes the sum of the given values. GROUP BY is a SQL clause that partitions rows into groups and computes a stated aggregate function for each group. Using these two functions together, you can compute total sums for a group of rows. In this article, we’ll see 8 different examples of how you can combine SUM() and GROUP BY to create many different reports.

Nicole Darnley

How to Use CASE WHEN in GROUP BY

Learn how you can combine SQL CASE WHEN and GROUP BY to create custom categories in your SQL queries. Raw data, by its very nature, is not always human readable. Many times, the data you’re querying is in its most unformatted form. Examples of this include codes for different business departments or product SKUs that represent specific products. To the naked eye, these codes mean nothing, so pulling them into a report is not helpful for the person reading them.

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.

Gustavo du Mortier

How to Group by Multiple Columns in SQL

When analyzing large data sets, you often create groupings and apply aggregate functions to find totals or averages. In these cases, using the GROUP BY clause with multiple columns unfolds its full potential. GROUP BY is a clause of the SELECT command. It allows you to compute various statistics for a group of rows. For example, you can use GROUP BY with an employee table to know how many employees are of each gender.

Nicole Darnley

How to Use WHERE with GROUP BY in SQL

In this article, we’ll discuss how to combine the WHERE and GROUP BY clauses in SQL. If you’re writing SQL on a daily basis, you will quickly realize how often both WHERE and GROUP BY clauses are used. WHERE is an essential part of most queries. It allows you to filter large datasets to only the pieces you are interested in. GROUP BY is one of the most powerful tools an analyst has when aggregating data.

Tihomir Babic

How to Use GROUP BY in SQL

In this article, we’ll give you a step-by-step guide on using GROUP BY in SQL. Uncover the nuances of the GROUP BY clause and learn different ways of using it. GROUP BY is one of the most-used clauses in SQL. It moves you from simply selecting data from the database to grouping rows with the same column values into one group. When used with SQL’s aggregate functions, you can use GROUP BY to compute metrics like counting the number of instances or finding the total, average, minimum, or maximum value.

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.

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?

Andrew Bone

How to Sort Values in a Specific Order in SQL

Sometimes you will be required to order your data in a particular way, and often the use of typical sort modifiers like ASC and DESC are not enough. This article will show you how to use the CASE statement to order your data exactly how you need it to be. Have you ever needed to order your data in a very specific way? One of the best methods for handling complex sorting is using CASE.

Himanshu Kathuria

Find Top Salaries by Department with SQL

This article shows how to get the total salary by department for an organization, using the GROUP BY functionality of SQL. We explain the SQL GROUP BY clause in detail along with conditional filtering using a HAVING clause. Understanding the salary outlay for an organization is one of the common starting points for business leaders. It helps them see who in the organization has the highest total salary cost, department-wise.

Andrew Bone

What Is the SQL GROUPING SETS Clause, and How Do You Use it?

GROUPING SETS are groups, or sets, of columns by which rows can be grouped together. Instead of writing multiple queries and combining the results with a UNION, you can simply use GROUPING SETS. GROUPING SETS in SQL can be considered an extension of the GROUP BY clause. It allows you to define multiple grouping sets in the same query. Let’s look at its syntax and how it can be equivalent to a GROUP BY with multiple UNION ALL clauses.

Marija Ilic

What Is GROUP BY in SQL?

GROUP BY is a great SQL feature that allows you to perform powerful calculations on grouped data. Do you want to learn how to get powerful insights from your data? Would you like to know what GROUP BY does and when you should use it? If your answer is yes, keep reading. In this article, you will learn exactly that. Why You Need GROUP BY In today's digitized world – no matter what business you are in – database tables are usually huge, with millions of records.

Agnieszka Kozubek-Krycuń

Why Aren’t SQL Window Functions Allowed in GROUP BY?

It’s true – the SQL order of operations means window functions aren’t allowed in GROUP BY. But you can use them anyway with this special trick. SQL window functions are one of the language’s most powerful features. However, the syntax of window functions is not easy to master. It has lots of details that can cause beginners to stumble. One of the most common traps is trying to use window functions in GROUP BY.

Marija Ilic

7 Common GROUP BY Errors

Are you making these errors with GROUP BY in SQL? Find out what they are, how to avoid them, and how to fix them. SQL’s GROUP BY statement can quickly uncover powerful data insights. At first, using GROUP BY can seem easy – e.g. when creating basic SQL reports that you’ll present to business decision-makers. But while learning this powerful feature, you could become trapped in weird errors or get incorrect results caused by improperly written GROUP BY statements.

How to Group by Two Columns in SQL

Problem You want to group your data by two columns so you can count some statistics. Example In the order table, you have the columns order_date, product_id, customer_id, and number. You would like to count the number of products bought by each customer each day. The order table looks like this: order_dateproduct_idcustomer_idnumber 2023-11-25711 2023-11-251213 2023-11-265312 2023-11-26124 2023-11-26321 2023-11-261627 2023-11-26332 2023-11-27631 Solution SELECT order_date, customer_id, SUM(number) AS products_number FROM order GROUP BY order_date, customer_id; The result is:

How to Group by Year in SQL

Problem You want to group your data by year in SQL. Example 1 One of the columns in your data is transaction_date. It contains a date. You would like to group all your data by year and calculate the total money earned each year. The data table looks like this: transaction_datemoney 2018-03-251700 2019-09-12100 2018-07-141200 2018-01-05400 2019-06-082000 2020-03-061500 Solution 1: Displaying the year and the money earned SELECT EXTRACT(year FROM transaction_date) AS year, SUM(money) AS money_earned FROM data GROUP BY EXTRACT(year FROM transaction_date); The result is:

Tihomir Babic

How to Use CASE WHEN With SUM() in SQL

This article will teach you what a CASE WHEN expression is in SQL and how to use it with a SUM() function and a GROUP BY statement. The examples are included to bolster your understanding. The best way to learn about CASE WHEN and how to use it with SUM() is our hands-on course Creating Basic SQL Reports. It contains over 90 interactive exercises that will teach you different techniques how to create complex reports in SQL.

Tihomir Babic

What is COUNT(*), COUNT(1), COUNT(column), and COUNT(DISTINCT) in SQL?

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.

Kateryna Koidan

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

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.

Kateryna Koidan

GROUP BY in SQL Explained

The SQL GROUP BY statement is easy to use, but it can be hard to master. Learn what you can do with GROUP BY, how it works, and how to use it with aggregate functions. GROUP BY is one of the basic SQL tools. However, it might be difficult for beginners to understand how GROUP BY works and how it is used to compute statistics with different aggregate functions. In this article, I’ll use several examples to show exactly how GROUP BY organizes rows and how aggregate functions can be used to calculate statistics on one or more columns.

Zahin Rahman

How to Find Duplicate Values in SQL — The Ultimate Guide

Find duplicate values in SQL efficiently and avoid wasting resources. This article demonstrates how to locate and address duplicate records using SQL's GROUP BY and HAVING clauses. Database best practices usually dictate having unique constraints (such as the primary key) on a table to prevent the duplication of rows when data is extracted and consolidated. However, you may find yourself working on a dataset with duplicate rows. This could be because of human error, an application bug, or uncleaned data that’s been extracted and merged from external sources, among other things.

Ignacio L. Bisso

How Does SQL GROUP BY Work?

Grouping results is a powerful SQL feature that allows you to compute key statistics for a group of records. GROUP BY is one of SQL’s most powerful clauses. It allows you to see data in a new way and find key metrics (like the average, maximal, and minimal values in a group of records). Without GROUP BY, all the results we obtain are oriented to records. With GROUP BY, we can create groups of records and calculate metrics on each group.

Adrian Więch

5 Examples of GROUP BY in SQL

Data grouping—or data aggregation—is an important concept in the world of databases. In this article, we’ll demonstrate how you can use the GROUP BY clause in practice. We’ve gathered five GROUP BY examples, from easier to more complex ones so you can see data grouping in a real-life scenario. As a bonus, you’ll also learn a bit about aggregate functions and the HAVING clause. SQL is a universal language to talk to databases that has been around for almost 50 years.

Dorota Wdzięczna

The SQL HAVING Clause Explained

What is the SQL HAVING clause? Why do you need it, and where do you use it? We’ll explain HAVING in detail. HAVING is a very common clause in SQL queries. Like WHERE, it helps filter data; however, HAVING works in a different way. If you are familiar with the GROUP BY clause and have only heard about HAVING – or if you’re not familiar with HAVING at all – this article is what you need.

Zahin Rahman

Using GROUP BY in SQL

Now that you know SQL’s core commands, power up your queries with the GROUP BY clause and aggregate functions. GROUP BY is a SQL clause that arranges data into groups based on a common value (or values). It is widely used to obtain summary information for large datasets as well as for computing basic aggregate statistics. Once you have grasped SQL’s basic commands like SELECT, WHERE, and JOIN, mastering the GROUP BY clause can help you implement your SQL knowledge in real-world business intelligence scenarios.

How to Order Rows by Group Sum in SQL

Problem: You’d like to order rows by the sums generated by a group of records. Example: Our database has a table named training with data in four columns: id, login, year, and score. idloginyearscore 1Andy201824 2Lucy201925 3Andy201920 4Lucy201816 5Gary201918 6Gary201819 7Gary201722 8Lucy201721 9Andy201726 Let’s get the login name of each player along with the total sum of score across all years, putting records in descending order according to players’ total scores.

Emil Drkušić

Differences Between GROUP BY and PARTITION BY

Window functions are a great addition to SQL, and they can make your life much easier if you know how to use them properly. Today, we will address the differences between a GROUP BY and a PARTITION BY. We’ll start with the very basics and slowly get you to a point where you can keep researching on your own. PARTITION BY vs. GROUP BY The PARTITION BY and the GROUP BY clauses are used frequently in SQL when you need to create a complex report.

Ignacio L. Bisso

HAVING vs. WHERE in SQL: What You Should Know

This article is about SQL’s WHERE and HAVING clauses. Both clauses are part of the foundations of the SQL SELECT command. They have similar uses, but there are also important differences that every person who uses SQL should know. Let’s see what’s behind the HAVING vs. WHERE debate. In this article, we’ll suppose we work for a government social agency supporting people or families whose income is below a certain threshold.

Shanika Wickramasinghe

Difference between GROUP BY and ORDER BY in Simple Words

For someone who is learning SQL, one of the most common places to get stuck is when learning the GROUP BY command. GROUP BY and ORDER BY are two important keywords in SQL that we use to organize data. The difference between GROUP BY and ORDER BY is that ORDER BY is more simple than GROUP BY and is usually introduced early in an SQL course. Sometimes, people are quite confused over these two concepts (SQL ORDER BY vs.

Belma Mesihovic

Grouping Data in SQL Server

People who work with data know that data grouping can sometimes be a chore. If you struggle and waste hours with Excel, OpenOffice, or some other tool trying to group various sets of data, take a look at this article and learn how to do the work much quicker and easier by using SQL. You often find yourself in a situation where you need to analyze data and present the results in a form other than the one in which the data is stored.

Maria Alcaraz

NULL Values and the GROUP BY Clause

We've already covered how to use the GROUP BY clause and some aggregation functions like SUM(), AVG(), MAX(), MIN(), COUNT(). In this article, we will explain how the GROUP BY clause works when NULL values are involved. We will also explain about using NULLs with the ORDER BY clause. The best way to master GROUP BY and NULL in SQL is through practice. I recommend the SQL Practice track at LearnSQL.

Jeffrey J. Keller

Grouping, Rolling, and Cubing Data

The first two articles in this series highlighted SQL Server's ability to organize data into user-defined windows and its aggregate functions. Part 3 will focus on other methods of aggregating and organizing data using built-in SQL Server features – specifically, its grouping functions. For consistency, the same base data will be used as in the first two parts of this series. CREATE TABLE WindowTable (WindowID INT IDENTITY, House Varchar(32), FullName Varchar(64), PhysicalSkill Decimal(4, 2), MentalSkill Decimal (4, 2)) GO