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Inner Join in SQL vs. Outer Join in SQL: What's the Difference?

Edited by Huma Saeed || By Sawaira Riaz || Published on February 4, 2024
An inner join in SQL returns rows where there is a match in both tables, while an outer join returns all rows from one table and matched rows from the other.

Key Differences

An inner join in SQL is used to return rows where there is at least one match in both tables being joined. An outer join, however, returns all rows from one table and the matched rows from the other, including rows with no match.
Sawaira Riaz
Feb 04, 2024
Inner join focuses on the intersection of two tables and excludes rows that do not have matching values. Outer join, in contrast, includes all rows from at least one of the tables, regardless of whether they have matching rows in the other table.
Sawaira Riaz
Feb 04, 2024
Inner joins typically result in fewer rows than outer joins, as they only include rows with matching values in both tables. Outer joins can return more rows, including those with no corresponding matches in the joined table.
Sawaira Riaz
Feb 04, 2024
The inner join is often used when only the matching data from both tables is required. Outer joins are useful when it's important to retain all records from one table, displaying NULL in columns where there's no match.
Harlon Moss
Feb 04, 2024
In terms of data completeness, an inner join provides a subset of data from both tables, whereas an outer join provides a more comprehensive view, including unmatched records.
Harlon Moss
Feb 04, 2024
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Comparison Chart

Match Requirement

Requires matching entries in both tables.
Includes all records from one table, match or no match.
Sawaira Riaz
Feb 04, 2024

Result Set

Only rows with matches in both tables.
All rows from one table, with or without matches.
Huma Saeed
Feb 04, 2024

Usage

Used when only matching data is needed.
Used to retain all records from one table.
Sawaira Riaz
Feb 04, 2024

Null Handling

Excludes rows with null values in join condition.
Includes rows with null values where no match is found.
Janet White
Feb 04, 2024

Typical Scenario

Ideal for matching related data across tables.
Useful for reports where data completeness is essential.
Janet White
Feb 04, 2024
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Inner Join in SQL and Outer Join in SQL Definitions

Inner Join in SQL

"Joins two tables based on a related column and excludes non-matching rows."
SELECT * FROM TableA INNER JOIN TableB ON TableA.key = TableB.key;
Harlon Moss
Jan 23, 2024

Outer Join in SQL

"A join that includes rows even if they don't have a matching counterpart."
SELECT Employees.Name, Departments.Name FROM Employees RIGHT OUTER JOIN Departments ON Employees.DeptID = Departments.ID;
Sawaira Riaz
Jan 23, 2024

Inner Join in SQL

"A join that retrieves rows with common values in both tables."
SELECT Employees.Name, Departments.Name FROM Employees INNER JOIN Departments ON Employees.DeptID = Departments.ID;
Huma Saeed
Jan 23, 2024

Outer Join in SQL

"An SQL join that fetches records even if join condition fails in one table."
SELECT A., B. FROM TableA A FULL OUTER JOIN TableB B ON A.common_field = B.common_field;
Janet White
Jan 23, 2024

Inner Join in SQL

"Returns rows where the join condition is true for both tables."
SELECT name, order_date FROM Customers INNER JOIN Orders ON Customers.id = Orders.customer_id;
Sawaira Riaz
Jan 23, 2024

Outer Join in SQL

"Combines rows from two tables, preserving unmatched rows from one table."
SELECT * FROM Customers LEFT OUTER JOIN Orders ON Customers.CustomerID = Orders.CustomerID;
Sawaira Riaz
Jan 23, 2024

Inner Join in SQL

"Combines rows from different tables when there are matching columns."
SELECT * FROM Customers INNER JOIN Orders ON Customers.CustomerID = Orders.CustomerID;
Sawaira Riaz
Jan 23, 2024

Outer Join in SQL

"Returns matched rows and unmatched rows from one or both tables."
SELECT name, order_date FROM Customers FULL OUTER JOIN Orders ON Customers.id = Orders.customer_id;
Sawaira Riaz
Jan 23, 2024

Inner Join in SQL

"An SQL join that fetches records with matching values in a join column."
SELECT A., B. FROM TableA A INNER JOIN TableB B ON A.common_field = B.common_field;
Aimie Carlson
Jan 23, 2024

Outer Join in SQL

"Joins tables while keeping the rows that don’t have matching join keys."
SELECT * FROM TableA LEFT OUTER JOIN TableB ON TableA.key = TableB.key;
Sawaira Riaz
Jan 23, 2024

FAQs

What does an outer join in SQL do?

An outer join in SQL returns all rows from one table and the matching rows from the other, including rows with no match.
Huma Saeed
Feb 04, 2024

What is a left outer join?

A left outer join returns all rows from the left table and matching rows from the right table.
Aimie Carlson
Feb 04, 2024

Can inner joins return null values?

Inner joins do not return rows with null join keys in either table.
Sawaira Riaz
Feb 04, 2024

What is an inner join in SQL?

An inner join in SQL is a join that returns rows with matching values in both joined tables.
Sawaira Riaz
Feb 04, 2024

Is a full outer join different from left and right outer joins?

Yes, a full outer join combines the results of both left and right outer joins.
Harlon Moss
Feb 04, 2024

Can outer joins be nested?

Yes, outer joins can be nested with other joins.
Aimie Carlson
Feb 04, 2024

Are inner joins faster than outer joins?

Inner joins can be faster as they return fewer rows compared to outer joins.
Sawaira Riaz
Feb 04, 2024

What's the difference between JOIN and INNER JOIN?

There's no difference; JOIN defaults to INNER JOIN in SQL.
Sawaira Riaz
Feb 04, 2024

When should I use an inner join?

Use an inner join when you need rows that have corresponding data in both tables.
Sawaira Riaz
Feb 04, 2024

What happens if the join condition is not met in an inner join?

In an inner join, rows that do not meet the join condition are not included in the result set.
Sawaira Riaz
Feb 04, 2024

Can I join more than two tables using inner or outer joins?

Yes, both inner and outer joins can be used to join multiple tables.
Aimie Carlson
Feb 04, 2024

What's a right outer join?

A right outer join returns all rows from the right table and matching rows from the left table.
Aimie Carlson
Feb 04, 2024

How do null values affect an inner join?

Null values in join columns prevent rows from being matched in an inner join.
Sawaira Riaz
Feb 04, 2024

What's a cross join?

A cross join is a Cartesian join that returns all possible pairs of rows from the joined tables.
Janet White
Feb 04, 2024

How do I choose between an inner and an outer join?

Choose based on whether you need all rows from one table (outer) or only matching rows (inner).
Sawaira Riaz
Feb 04, 2024

Can outer joins result in duplicate rows?

Yes, outer joins can result in duplicate rows if there are multiple matches in the joined table.
Aimie Carlson
Feb 04, 2024

How are unmatched rows represented in an outer join?

In an outer join, unmatched rows are shown with NULLs in columns from the table where there is no match.
Sawaira Riaz
Feb 04, 2024

Do I need to use the OUTER keyword for outer joins?

The OUTER keyword is optional as LEFT JOIN is equivalent to LEFT OUTER JOIN.
Harlon Moss
Feb 04, 2024

Is it possible to filter results in an outer join?

Yes, you can use the WHERE clause to filter results in an outer join.
Sawaira Riaz
Feb 04, 2024

Can I use aggregate functions with inner and outer joins?

Yes, aggregate functions can be used with both inner and outer joins.
Sawaira Riaz
Feb 04, 2024
About Author
Written by
Sawaira Riaz
Sawaira is a dedicated content editor at difference.wiki, where she meticulously refines articles to ensure clarity and accuracy. With a keen eye for detail, she upholds the site's commitment to delivering insightful and precise content.
Edited by
Huma Saeed
Huma is a renowned researcher acclaimed for her innovative work in Difference Wiki. Her dedication has led to key breakthroughs, establishing her prominence in academia. Her contributions continually inspire and guide her field.

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