Mike's Notes
Another gem from Neo Kim. I'm a visual learner and like the use of Venn Diagrams in the sketch.
Resources
- https://substack.com/@systemdesignone/note/c-160744694
- https://www.w3schools.com/sql/default.asp
- https://en.wikipedia.org/wiki/Venn_diagram
- https://en.wikipedia.org/wiki/Join_(SQL)
- https://learnsql.com/blog/sql-joins/
- https://www.codeproject.com/articles/Visual-Representation-of-SQL-Joins
References
- Reference
Repository
- Home > Ajabbi Research > Library > Subscriptions > The System Design Newsletter
- Home > Handbook >
Last Updated
07/10/2025
How SQL JOINs work
By: Neo Kim
The System Design Newsletter: 01/10/2025
(explained in 2 mins or less):
- Inner join
It returns rows with matching values in both tables - Full outer join
It returns all rows when there is a match in either the left or the right table - Full outer exclusive
It returns all rows from both tables with no match in the other table - Left join
It returns all rows from the left table and matched rows from the right table - Left exclusive
It returns rows from the left table with no match in the right table - Right join
It returns all rows from the right table and matched rows from the left table - Right exclusive
It returns rows from the right table with no match in the left table - Cross join
It returns the Cartesian product of both tables; every combination of rows - Self join
It joins a table with itself to compare rows within the same table
The JOIN clause lets you combine data from tables based on a related column.
What else?
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