RIGHT OUTER JOIN

A RIGHT OUTER JOIN is one of the JOIN operationss that allow you to specify a JOIN clause. It preserves the unmatched rows from the second (right) table, joining them with a NULL in the shape of the first (left) table. A LEFT OUTER JOIN B is equivalent to B RIGHT OUTER JOIN A, with the columns in a different order.

Syntax

TableExpression RIGHT [ OUTER ] JOIN TableExpression
{
    ON booleanExpression 
    }

The scope of expressions in the ON clause includes the current tables and any tables in query blocks outer to the current SELECT. The ON clause can reference tables not being joined and does not have to reference either of the tables being joined (though typically it does).

Example 1

-- get all countries and corresponding cities, including
-- countries without any cities

SELECT COUNTRIES.COUNTRY, CITIES.CITY_NAME 
FROM CITIES 
RIGHT OUTER JOIN COUNTRIES 
ON CITIES.COUNTRY_ISO_CODE = COUNTRIES.COUNTRY_ISO_CODE;

-- get all countries in Africa and corresponding cities, including
-- countries without any cities

SELECT COUNTRIES.COUNTRY, CITIES.CITY_NAME
FROM CITIES 
RIGHT OUTER JOIN COUNTRIES 
ON CITIES.COUNTRY_ISO_CODE = COUNTRIES.COUNTRY_ISO_CODE
WHERE Countries.region = 'Africa';

-- use the synonymous syntax, RIGHT JOIN, to achieve exactly
-- the same results as in the example above

SELECT COUNTRIES.COUNTRY, CITIES.CITY_NAME
FROM CITIES 
RIGHT JOIN COUNTRIES 
ON CITIES.COUNTRY_ISO_CODE = COUNTRIES.COUNTRY_ISO_CODE
WHERE Countries.region = 'Africa';

Example 2

-- a TableExpression can be a joinOperation. Therefore
-- you can have multiple join operations in a FROM clause
-- List every employee number and last name 
-- with the employee number and last name of their manager

SELECT E.EMPNO, E.LASTNAME, M.EMPNO, M.LASTNAME	
	FROM EMPLOYEE E RIGHT OUTER JOIN	
	DEPARTMENT RIGHT OUTER JOIN EMPLOYEE M 
        ON MGRNO = M.EMPNO
        ON E.WORKDEPT = DEPTNO;