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Are you looking forward to a programming interview soon? Then take a few moments to look over one of the most common question interviewers will ask you. The dissimilarity between inner join vs outer join is our primary focus in this post. Therefore, we’ll equip you with enough information to help you ace your interview.
Inner Join vs Outer Join
A join in SQL contrasts, links, and outputs particular rows of data from one table to the other. It can also work across multiple tables in a file. The major point of distinction between an inner and outer join is that the inner join locates and outputs similar records from tables while the outer join locates and outputs similar data and other dissimilar records from tables.
How Inner Join Works
You can consider a scenario of two tables, for instance, student details and school database table. The two tables have one common column: the student names. Therefore, it will act?as the logical column on which to base the join. The inner join will thus return the information common to the two tables; that is the student name.
How the Outer Join Works
The outer join outputs a set of records that consists of the common data among two tables as well as other rows unique to a single table within the join. The outer join is further categorized into three; left, right and full outer joins.
- Left outer join: returns all data in the first table, all the shared data among the two tables and just the corresponding data from the second table in the right join.
- Right outer join: returns all the information in the second table, the shared data and just the corresponding data from table one in the left join.
- Full outer join: it combines and shares all the data from the two or multiple tables. Usually, it is not used in MySQL database.
These two join types are usually formed based on a predicate that specifies the regulations to be used when performing the join.
Therefore, you should use the inner join only if you want records that have matching records in both tables involved in a join. The outer join is applicable when you want to see all the records in one table and any possibly matching records on the second table.
We hope that you can quickly identify the key difference between inner join and outer join through this article to enable you to ace your interview regarding SQL servers. We hope you will participate with your comments or thoughts on our exploration of the inner vs outer join.