Top 10 SQL JOIN Articles for Beginners

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. And they’re mostly intended for absolute beginners.

What Are SQL JOINs?

A JOIN is an SQL clause that allows you to connect two or more tables; thus, you can get data from all the tables that are joined together. Tables are joined based on columns in both (or all) tables that share the same values. For example, if you had an id column in the author table, you could also have author_id columns in the book and series tables. These three columns would share the same values (i.e. the same author ID numbers) and could be used to combine data from all three tables.

SQL JOIN Types

There are four main JOIN types you’ll read about. They are:

• INNER JOIN
• LEFT JOIN
• RIGHT JOIN
• FULL OUTER JOIN

Knowing what every JOIN type does is essential for mastering them. You’ll read more about this in the articles below. So, which articles will help you in understanding these JOINs?

Top 10 SQL JOIN Articles for Absolute Beginners

1. Joining Data Tables: The Basics

Author: Nicole Hitner

Link: https://exagobi.com/reporting/joining-data-tables-the-basics

Description:

Exago, a web-based embedded business intelligence software company, published this article on their blog. This is an article with no SQL code. Instead, it leads you very elegantly through the logic of SQL JOINs. You’ll first learn what primary and foreign keys are, which is necessary to understand how joining tables works. After that, the article will explain how every JOIN works and what data you’ll get when you use it. It does all that with a very nice mix of verbal and visual explanations.

Why it’s useful: 

It won’t distract you with the syntax and the SQL code. The article is focused on explaining the logic of the SQL JOINs, which you should know before you jump into writing code. It’s nicely presented and contains everything a beginner needs. And it’s useful for understanding relational database logic in general.

2. Get Started With SQL JOINs

Author: Destin Gong

Link: https://towardsdatascience.com/get-started-with-sql-joins-87835422644b

Description:

This article was published on Towards Data Science’s blog on Medium. It uses a different approach to explain JOINs. It goes one step back to make you aware that you’ve probably already used joins without realizing it. (Spoiler: If you use the VLOOKUP function in Excel, you’re joining tables.) The author explains the SQL JOIN syntax and gives you an example of simple SQL code.  They also discuss all four JOINs, again giving you examples for every type and a thorough explanation of the code.

Additionally, this article will also show you the fifth join type: the cross join.

Why it’s useful: 

It shows you the JOIN syntax and provides example code for every join type. It’s especially helpful for someone shifting from Excel to SQL because it explains JOINs logic using an Excel example.

3. SQL JOIN Cheat Sheet

Author: LearnSQL.com Team

Link: https://learnsql.com/blog/sql-join-cheat-sheet/

Description:

This one is LearnSQL.com’s own cheat sheet, and it’s a very helpful one for anybody learning SQL JOINs or simply wanting to have all that JOIN info at a glance. That’s why this cheat sheet is more graphic than it is textual. It provides you with quick overviews, explanations, and examples of the JOIN types. Along with the four standard JOINs, it also covers the natural join, cross join, self join, non-equi self join, and multiple joins. On top of all that, there’s helpful information on how to use column and table aliases.

Why it’s useful: 

This cheat sheet is visually attractive. It’s easy to understand while still giving you enough information on SQL JOINs. There’s always an example code to remind you how a particular JOIN works and how to use it with aliases.

4. SQL Natural Join

Author: Ian

Link: https://database.guide/sql-natural-join/

Description:

Now that you’ve learned there’s a natural join, maybe you want to practice it a little bit. Or maybe you’d like to use it with other joins. This article from Database.Guide (a blog about database concepts for beginners) could be of some use. It explains how to use natural inner joins and natural right joins. The author also shows you how to join three tables using the NATURAL FULL JOIN clause. Finally, the fourth example teaches you how to use the asterisk (*) wildcard character with a natural join.

Why it’s useful: 

This article goes more into detail about natural joins. There’s not much beating around the bush; it shows you the example SQL code and what results it returns. By learning how to combine natural joins with other joins, you can start thinking less rigidly about SQL JOINs.

5. Inner Join Vs. Outer Join: Examples With SQL Queries

Author: Temok Team

Link: https://www.temok.com/blog/inner-join-vs-outer-join/

Description:

After getting to know every JOIN type, it’s time to dig a little deeper. This article focuses on explaining the differences between INNER JOIN and OUTER JOIN. This blog post from Temok is very well-written and details the differences between those two types of joins. It’s also immensely graphically pleasing, explaining the logic using Venn diagrams and table pictures. It not only shows you how to use inner and outer joins, it also compares their performance and reliability.

Why it’s useful: 

This post is written in very straightforward language and it doesn't lose itself in technicalities. The explanations are clear and help readers understand the difference between joins. There’s also a comparison table at the end that gives you a good overview of those differences.

6. The Difference Between SQL’s JOIN ... ON Clause and the WHERE Clause

Author: Lukas Eder

Link: https://blog.jooq.org/2019/04/09/the-difference-between-sqls-join-on-clause-and-the-where-clause/

Description:

This one is published on jOOQ’s blog. jOOQ is a Java database library, and they have some very high-quality articles about SQL on their blog. This one explores the differences between the ON and WHERE clauses. The two clauses are explained using examples, and the results are discussed very clearly.

Why it’s useful: 

The differences between WHERE and ON are explained using not-too-complicated examples, which is important as these two clauses can seem the same to beginners. The article ends by nicely outlining the general overview of the differences and gives you some tips on when to use each clause.

7. An Overview of SQL Join Types with Examples

Author: Rajendra Gupta

Link: https://www.quest.com/community/blogs/b/database-management/posts/an-overview-of-sql-join-types-with-examples

Description:

Using very detailed graphics, this article will provide you with an overview of all SQL JOINs. It’s nice to have as a reminder, especially if you’re a beginner. It will give you an overview of how inner join, self-join, cross join, and outer joins (left, right, and full) work. There’s also a very good explanation of using JOINs with multiple tables. Finally, the article closes with a list of SQL JOIN best practices worth following. This article was published by Quest, an IT company offering data and database-related software and services.

Why it’s useful:  

There is an excellent graphical representation of SQL JOINs that doesn’t require very detailed explanations. The article also mentions NULL values and joining multiple tables.

8. A Step-by-Step Walkthrough of SQL Inner Join

Author: Gauri Mahajan

Link: https://www.sqlshack.com/a-step-by-step-walkthrough-of-sql-inner-join/

Description:

Here’s an article that goes straight to explaining the nuances of INNER JOIN. You’ll get a detailed definition and see how it works on an example, with a very clear explanation of the SQL query results. Additionally, the article will show you how to join three tables and use the WHERE and GROUP BY clauses with INNER JOIN. Also, there’s an explanation of equi and non-equi joins (or theta joins). The article is published on SQL Shack, a website sharing SQL knowledge.

Why it’s useful: 

Less theory, more practical examples. This article provides you with the code to create the example tables so you can practice on them yourself. Plus, it teaches you how to use INNER JOIN with other SQL clauses, which is closer to what you’ll do in real life.

9. More Dangerous Subtleties of JOINs in SQL

Author: Alex Petralia

Link: https://alexpetralia.com/posts/2017/7/19/more-dangerous-subtleties-of-joins-in-sql

Description:

This one’s a little bit different; it’s not an article where you’ll get detailed explanations of various joins. But if you already know something about SQL JOINs, this article will teach you how to avoid some mistakes. It covers semantic errors, i.e. join duplications and what the author calls ‘join misses’. This article is published on Alex Petralia’s website.

Why it’s useful: 

It prepares you for the practical use of joins. Knowing how to join tables is one thing; getting the desired (and correct!) results is sometimes completely different! This article will teach you how to approach your data when you use JOINs. This is beneficial, especially if you don’t have much actual experience with SQL.

10. How to Join 3 Tables (or More) in SQL

Author: Kamil Bladoszewski

Link: https://learnsql.com/blog/how-to-join-3-tables-or-more-in-sql/

Description:

I’ve listed quite enough articles that give you an overview of the SQL JOIN types. This one concentrates on showing you how to join three or more tables. It starts by showing the data that will be used on the example JOINs. Then it explains what a junction table is (in case you’ve never run into one yet). The author will show you how to join three tables using the junction table in a very clear way. Then you’ll do the same, but without the junction table. Finally, there’s a graphic representation showing you how multiple joins work and how you get from three tables to the result you want. This article is also by LearnSQL.com.

Why it’s useful: 

This article leads you step-by-step through the process of multiple joins. Once you learn how to join three of them, you’ll be able to join any number of tables.

Where to Find More Info About SQL JOINs

Reading ten good articles is a good start for anybody who is learning SQL JOINs. Generally, most of the articles focus on explaining how JOINs work, what they are, and the differences between various types. Once you get the basics, you can always look for more advanced articles covering specific JOIN issues.

It’s also highly advisable to practice joining tables in SQL. While the articles offer some basic examples, it’s always good to write your own queries. If you’re still learning or want a platform for extended SQL practice, our SQL JOINs course will give you what you need.