A Visual Explanation of SQL Joins

Thank you so much for making this available. Cheers from the UK

This article is great! A picture is worth a thousand words, and your pictures have helped me to understand SQL joins. Thanks.

Hey that was a CLEAR explanation … just started up with sqlite
and didnt get why i was not getting the selection i wanted.

Now i do!

how do you join two columns together and get one column in a query. For EX: i have lastname and firstname columns in a table. i want to join these two columns together and get lastname and firstname in one column ??

Although I’m familiar with the topic, I still like your nice and easy way of explaining things, nice work.

This was a GREAT explanation. I am working with a junior DBA and this has helped tremendously. I will have to go back and read some of your other blogs.


As someone suggested to created something themselves and then criticize :wink: I’ve tried to describe relationships among various join types using ER diagramm here:
All comments welcome!

It’s a great way to explain things…

Thanks for this Jeff, was struggling a bit with the concept but you’ve made it clear enough that even I can get my head around it :slight_smile:

I really have to hand it to you Jeff, the way you break things down is just great. I read the blogs every time you post one. This one in particular came in handy just the other day. Our QA team was having trouble understanding what was going on in the database and we developers would send them queries to run to find the data they needed. The QA team has a rudimentary understanding of SQL, but couldn’t quite grasp joins. I sent a link to this article to our lead QA, and now your article is firmly posted on her cube wall for reference. Just wanted to say thank you for the blogs!

Years ago I had diagrams like this posted on my desk and I refered to it nearly every other day. Thank you for posting this as I am sure I will be refering to it often as I try to understand and explain to others the impacts of SQL statements

This has been extremely helpful for a project that I am currently working on. I am by no means a coding expert(not a novice either), but there is a lot of stuff I have yet to learn. The way this is all displayed with the use of venn diagrams has made it very easy to understand, thanks for the help.

This page is so helpful!

I am constantly needing to build MySQL queries for my php and .net applications and I come back to this page time and time again to prevent me from having to think too hard!

Just that one less moment spent on these details when you’re in the middle of solving big problems makes all the difference.

Thank you!

hi jeff,
Thanks a lot for this ven diagram explanation. i opened the website without any understanding on sql joins and after reading ur explanation, i’ve understood it so well. really very helpfull.
Thanks a lot!

Great explain, thanks a lot.

Its nice way of explanation of SQL Joins .Too easy!

Excellent way of exhibiting the concept.
Simple , easy to understand.

Great and very simply to understand!

Great Work, Im teacher, and Iwill use this, to explain de joins.

Explained very well. Helped me a lot