Oracle Database Interview Question:

How To Write a Query with a Right Outer Join in Oracle?

Submitted by: Administrator

If you want to query from two tables with a right outer join, you can use the RIGHT OUTER JOIN ... ON clause in the FROM clause. The following query returns output with a right outer join from two tables: departments and employees. The join condition is that the manager ID in the departments table equals to the employee ID in the employees table:

SQL> set NULL 'NULL'
SQL> SELECT d.department_name, e.first_name, e.last_name
2 FROM departments d RIGHT OUTER JOIN employees e
3 ON d.manager_id = e.employee_id;
<pre>DEPARTMENT_NAME FIRST_NAME LAST_NAME
-------------------- -------------------- ---------------
Administration Jennifer Whalen
Marketing Michael Hartstein
Purchasing Den Raphaely
Human Resources Susan Mavris
Shipping Adam Fripp
IT Alexander Hunold
......
NULL Clara Vishney
NULL Jason Mallin
NULL Hazel Philtanker
NULL Nanette Cambrault
NULL Alana Walsh
NULL Karen Partners
NULL Bruce
Submitted by: Administrator

Note that a right outer join may return extra rows from the second (right) table that do not satisfy the join condition. In those extra rows, columns from the first (left) table will be given null values.

The extra rows returned from the right outer join in this example represents employees that are not assigned as managers in the departments table.
Submitted by: Administrator