Inner Join vs. Outer Join: Know the Difference
By Shumaila Saeed || Published on February 6, 2024
Inner Join combines rows from different tables based on a related column, showing only matching rows. Outer Join includes all rows from one or both tables, filling in with nulls where no match exists.
Key Differences
Inner Join in SQL is a type of join that returns rows from multiple tables where the join condition is met. It only includes rows where the specified columns in both tables match. Conversely, an Outer Join also includes rows where the join condition is not met. In an Outer Join, if no matching rows are found in one table, the result set will still include the rows from the other table, with nulls for the missing values.
Shumaila Saeed
Feb 06, 2024
The Inner Join is more restrictive, as it filters out rows that do not have corresponding data in both tables. It's often used when only the data present in all joined tables is required. On the other hand, an Outer Join is more inclusive, allowing for the retention of all the rows from one or both tables. It's ideal when you need to preserve the complete data set from one or both tables, even if they don't match perfectly.
Shumaila Saeed
Feb 06, 2024
In an Inner Join, the resulting dataset is usually smaller because it contains only the rows that have matching values in both tables. This makes Inner Joins efficient for datasets where a strict match is necessary. Outer Joins, in contrast, produce a larger dataset, as they include all rows from one or both tables, filled with nulls for non-matching columns. This can be useful for identifying missing or unmatched data.
Shumaila Saeed
Feb 06, 2024
An Inner Join typically requires a condition, often where a column in one table equals a column in another. Without a match, the row isn't included in the result. An Outer Join, which can be left, right, or full, does not have this restriction. A Left Outer Join includes all rows from the left table, and a Right Outer Join includes all from the right, while a Full Outer Join includes all rows from both, regardless of matching.
Shumaila Saeed
Feb 06, 2024
Lastly, Inner Joins are generally faster and more efficient because they deal with less data after the join. Outer Joins, although more comprehensive, can be slower, especially Full Outer Joins, as they need to process and include all rows from the joined tables, matching or not.
Shumaila Saeed
Feb 06, 2024
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Comparison Chart
Matching Criteria
Includes only rows with matching values in both tables.
Includes all rows, matching or not, from one/both tables.
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Feb 06, 2024
Result Set Size
Typically smaller, as it only contains matching rows.
Larger, includes non-matching rows, filled with nulls.
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Feb 06, 2024
Use Case
Used when data in all joined tables is required.
Used to retain complete data from one/both tables.
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Feb 06, 2024
Null Handling
Excludes nulls unless explicitly matched.
Includes nulls for non-matching columns.
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Feb 06, 2024
Efficiency
Generally faster due to less data post-join.
Can be slower, especially Full Outer Joins.
Shumaila Saeed
Feb 06, 2024
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Inner Join and Outer Join Definitions
Inner Join
Inner Join filters data to include only rows with corresponding matches in the join condition.
Using an Inner Join on employee and department tables ensures only employees currently assigned to departments are listed.
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Jan 25, 2024
Outer Join
A join method for combining tables where not all rows need a corresponding match.
The Outer Join between the product and sales tables revealed products that have never been sold.
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Jan 25, 2024
Inner Join
Inner Join is a default SQL join, linking tables where column values intersect.
The database query performed an Inner Join on user IDs to correlate user data across tables.
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Outer Join
Outer Join can be a Left, Right, or Full Join, each including unmatched rows from one or both tables.
A Left Outer Join was used to list all students and their optional course enrollments.
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Jan 25, 2024
Inner Join
A query operation that combines columns from related tables, based on matched data.
The report used an Inner Join to combine data from the sales and product tables based on product IDs.
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Jan 25, 2024
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Outer Join
Outer Join includes rows with no corresponding match in the other table.
The report used an Outer Join to show all inventory items, even those without sales records.
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Jan 25, 2024
Inner Join
A join returning rows where there are matching values in both joined tables.
The Inner Join of customer and order tables shows only customers who have placed orders.
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Jan 25, 2024
Outer Join
A join that returns all rows from at least one of the tables, matched or unmatched.
An Outer Join on the employee and project tables lists all employees, including those not currently on a project.
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Jan 25, 2024
Inner Join
Inner Join forms a result set of records that have matching values in both tables.
An Inner Join on the book and author tables displays all books with their respective authors.
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Jan 25, 2024
Outer Join
A SQL operation that merges rows from two tables, filling in missing matches with nulls.
Using an Outer Join, the query displayed all customer orders, including those with no corresponding shipment details.
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Jan 25, 2024
Repeatedly Asked Queries
When is an Inner Join used?
Inner Join is used when you need to combine rows from two tables and only want the rows that have matching values in both.
Shumaila Saeed
Feb 06, 2024
Can an Outer Join be used to find unmatched rows?
Yes, an Outer Join is often used to find rows in one table that do not have corresponding rows in another table.
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Feb 06, 2024
How does an Inner Join handle null values?
Inner Join typically excludes rows with null values in the join condition unless they are explicitly matched.
Shumaila Saeed
Feb 06, 2024
Which is faster, Inner Join or Outer Join?
Inner Join is generally faster because it deals with fewer rows after the join.
Shumaila Saeed
Feb 06, 2024
Is an Inner Join more restrictive than an Outer Join?
Yes, an Inner Join is more restrictive as it only returns rows with matching data in both tables.
Shumaila Saeed
Feb 06, 2024
What is an Inner Join?
An Inner Join is a type of database join where only the rows that have matching values in both joined tables are returned.
Shumaila Saeed
Feb 06, 2024
Can Outer Joins create larger result sets?
Yes, Outer Joins often create larger result sets as they include all rows from one or both tables, regardless of matches.
Shumaila Saeed
Feb 06, 2024
What is an Outer Join?
An Outer Join is a database join that returns all rows from one or both tables, with unmatched rows filled in with nulls.
Shumaila Saeed
Feb 06, 2024
What are the types of Outer Joins?
Outer Joins can be Left, Right, or Full, depending on which table's rows are included when there's no match.
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Feb 06, 2024
How does an Inner Join affect query performance?
Inner Joins can improve query performance by reducing the size of the result set through filtering non-matching rows.
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Feb 06, 2024
Is it possible to combine Inner and Outer Joins in a query?
Yes, you can combine Inner and Outer Joins in a single query to achieve complex data retrieval.
Shumaila Saeed
Feb 06, 2024
Does an Outer Join include non-matching rows?
Yes, an Outer Join includes non-matching rows, filling in missing data with nulls.
Shumaila Saeed
Feb 06, 2024
What is the default join in SQL?
The default join in SQL is the Inner Join.
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Feb 06, 2024
What is a Left Outer Join?
A Left Outer Join includes all rows from the left table, and matched rows from the right table, with nulls for unmatched right table rows.
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Feb 06, 2024
Can Outer Joins be used for data analysis?
Yes, Outer Joins are useful in data analysis for identifying gaps or discrepancies between related data sets.
Shumaila Saeed
Feb 06, 2024
How does an Inner Join impact data integrity?
Inner Join maintains data integrity by only returning rows where the join condition is valid in both tables.
Shumaila Saeed
Feb 06, 2024
How does a Full Outer Join work?
A Full Outer Join returns all rows from both tables, with non-matching rows filled in with nulls.
Shumaila Saeed
Feb 06, 2024
What is a Right Outer Join?
A Right Outer Join includes all rows from the right table, and matched rows from the left table, with nulls for unmatched left table rows.
Shumaila Saeed
Feb 06, 2024
Do Inner Joins eliminate duplicate rows?
Inner Joins do not automatically eliminate duplicate rows; they only return rows where the join condition matches in both tables.
Shumaila Saeed
Feb 06, 2024
Are Outer Joins suitable for all types of data relationships?
Outer Joins are suitable for exploring data relationships, especially when you need to include rows that don't have matches in related tables.
Shumaila Saeed
Feb 06, 2024
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About Author
Written by
Shumaila SaeedShumaila Saeed, an expert content creator with 6 years of experience, specializes in distilling complex topics into easily digestible comparisons, shining a light on the nuances that both inform and educate readers with clarity and accuracy.
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