What is the difference between inner join and outer join?
Joins in SQL are typically used to combine and compare contents. The data can be joined in many ways such as inner join, full outer join, left outer join, and right outer join.
The main difference between inner join and outer join is that the former finds and returns matching data from tables while the latter finds and returns matching data and some dissimilar data from tables.
Comparison Table (Inner Join vs Outer Join)
|Inner Join||Outer Join|
|It returns the combined tuple between two or more tables.||It returns the combined tuple from a specified table even join condition will fail.|
|Used clause INNER JOIN and JOIN.||Used clause LEFT OUTER JOIN, RIGHT OUTER JOIN, FULL OUTER JOIN, etc.|
|When any attributes are not common then it will return nothing.||It does not depend upon the common attributes. If the attribute is blank then here already placed NULL.|
|Tend to work faster||Tend to work slower|
|It is used when we want detailed information about any specific attribute.||It is used when we want to complete information.|
|JOIN and INNER JOIN both clauses work the same.||FULL OUTER JOIN and FULL JOIN both clauses work the same.|
from table1 INNER JOIN / JOIN table2
ON table1.column_name = table2.column_name;
from table1 LEFT OUTER JOIN / RIGHT OUTER JOIN /
FULL OUTER JOIN / FULL JOIN table2 ON
table1.column_name = table2.column_name;
What Is Inner Join?
It is an SQL join used to combine data from two or more tables based on common fields between them. The join typically finds matching or overlapping data and combine them in one table.
Example of an Inner Join:
INNER JOIN StudentCourse
ON StudentCourse.EnrollNo = Student.EnrollNo
ORDER BY StudentCourse.CourseID
What Is Outer Join?
It is an SQL join that returns a combined tuple from a specified table even the join condition will fail. It is further divided into Left Outer Join, Right Outer Join, and Full Outer Join.
Example of Outer Join include:
from table1 LEFT OUTER JOIN table2
on table1.column_name = table2.column_name;
Main Difference between Inner Join and Outer Join
- Inner join load faster while outer join loads slower
- Join and Inner join work the same way while full outer and full join work the same
- Inner join provide detailed information about specific attributes while outer join is used to complete information
- Inner join return nothing if attributes are not common whereas outer join return null if the attribute is blank
Understanding the difference between inner join and outer join in SQL will enable you perform your assignments without any problem. Feel free to listen to the podcast since it has more detailed and explained information about these two SQL joins.
More Sources and References
- SQL Join. Wikipedia
- Inner Join. Microsoft Server
- Outer Join. Microsoft Server