Inner Join vs. Outer Join — What's the Difference?
Edited by Tayyaba Rehman — By Fiza Rafique — Published on January 9, 2024
Inner Join returns rows where there's a match in both tables; Outer Join returns rows with matches and unmatched rows from one or both tables.
Difference Between Inner Join and Outer Join
Table of Contents
ADVERTISEMENT
Key Differences
Inner Join and Outer Join are techniques used in relational databases to combine rows from two or more tables based on related columns. The Inner Join specifically returns only rows where there is a match in both the tables involved. In other words, if a record in Table A matches a record in Table B based on the join condition, the Inner Join will display it.
Outer Join, on the other hand, can return rows even if there is no match in one or both tables. Depending on its type (Left, Right, or Full), the Outer Join can return all the rows from one table and matching rows from another, or it can return all rows from both tables with matches wherever available.
When using an Inner Join, it's possible to lose data that doesn't have corresponding matches in both tables. For instance, if Table A has data that doesn't find a match in Table B, that data won't be included in the result. The Outer Join ensures that this data isn't lost, as it can display unmatched rows too.
While the Inner Join often leads to smaller result sets due to its strict matching condition, the Outer Join provides a more comprehensive overview, including data from one or both tables, matched or unmatched. It's important to note that the type of join chosen can significantly affect the outcome and the information presented in the result set.
Comparison Chart
Basic Function
Returns matched rows from both tables.
Returns matched rows and unmatched rows from one or both tables.
ADVERTISEMENT
Result Set Size
Typically smaller, only matched rows.
Larger, includes matches and unmatched rows.
Data Loss
Can lead to data loss if no match.
Prevents data loss by displaying unmatched rows.
Types
Just one type.
Three types: Left, Right, and Full.
Application
When only wanting intersecting data.
When a more comprehensive overview including non-intersecting data is required.
Compare with Definitions
Inner Join
Inner Join can potentially exclude rows without matches.
Employees without departments were left out in the Inner Join result.
Outer Join
Outer Join offers a more inclusive result than Inner Join.
The Outer Join displayed all items, even those not sold.
Inner Join
Inner Join combines rows from tables where there's a match in both.
Using an Inner Join, the query only displayed students enrolled in courses.
Outer Join
Outer Join ensures no data is overlooked in the result.
Using Outer Join, both active and inactive users were listed.
Inner Join
Inner Join is strict in its output, ensuring every row meets the join condition.
The Inner Join gave us a list of clients who have both orders and account details.
Outer Join
Outer Join can be of three types: Left, Right, and Full.
A Left Outer Join showed all students, whether they had grades or not.
Inner Join
Inner Join leads to results strictly based on matching criteria.
With Inner Join, only products with sales records were shown.
Outer Join
Outer Join retrieves matched rows and unmatched rows from tables.
Using an Outer Join, we saw all employees, regardless of their current project assignments.
Inner Join
Inner Join operates on the intersection of datasets.
The Inner Join provided results only for books that were both sold and in stock.
Outer Join
Outer Join gives a holistic view, combining matched and unmatched data.
The Outer Join provided a comprehensive list of authors, with or without published articles.
Common Curiosities
How is an Outer Join different from an Inner Join?
While an Inner Join only returns matched rows from both tables, an Outer Join returns matched rows and unmatched rows from one or both tables.
How many types of Outer Join are there?
There are three types of Outer Join: Left, Right, and Full.
When should I use an Inner Join?
Use an Inner Join when you only want to see rows where there's a match in both tables.
Can Inner Join result in data loss?
Yes, Inner Join can exclude rows that don't have matches in both tables.
If I use a Right Outer Join, which table's unmatched rows will be shown?
A Right Outer Join displays all rows from the second (right) table and the matched rows from the first (left) table.
Can Outer Join provide a comprehensive dataset?
Yes, Outer Join provides a more comprehensive overview by including matched and unmatched data.
Do both Inner Join and Outer Join require a join condition?
Yes, both Inner Join and Outer Join operate based on a specified join condition.
Is there a risk of data duplication with Inner Join?
Both Inner Join and Outer Join can result in data duplication if there are multiple matching rows in the joined tables.
What does an Inner Join do?
An Inner Join returns rows where there's a match in both tables based on a specified condition.
Is Inner Join typically faster than Outer Join?
Generally, Inner Join can be faster due to returning fewer rows, but performance depends on specific data and indexing.
Share Your Discovery
Previous Comparison
Greek Gods vs. Roman Gods
Next Comparison
Sassy vs. ClassyAuthor Spotlight
Written by
Fiza RafiqueFiza Rafique is a skilled content writer at AskDifference.com, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.
Edited by
Tayyaba RehmanTayyaba Rehman is a distinguished writer, currently serving as a primary contributor to askdifference.com. As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.
