Retrieving Records with Natural Joins

In the example on the slide, the LOCATIONS table is joined to the DEPARTMENT table by the LOCATION_ID column, which is the only column of the same name in both tables. If other common columns were present, the join would have used them all.

Equijoins

The natural join can also be written as an equijoin:

SELECT department_id, department_name,
departments.location_id, city
FROM departments, locations
WHERE departments.location_id = locations.location_id;

Natural Joins with a WHERE Clause Additional restrictions on a natural join are implemented by using a WHERE clause. The example below limits the rows of output to those with a department ID equal to 20 or 50.

SELECT department_id, department_name,
location_id, city
FROM departments
NATURAL JOIN locations
WHERE department_id IN (20, 50);