Example 3: Outer Join That Is Really an Inner Join - Teradata Database

Example 3 is another query where an explicit outer join is specified, but that join is logically an inner join, so the Optimizer transforms it into a simple inner join before performing the query.

     SELECT c.custnum, b.monthly_revenue

     FROM sampdb.customer c

     LEFT OUTER JOIN sampdb2.revenue b ON c.custnum = b.custnum

     AND  c.district ='K'

     AND (c.service_type = 'ABC' 

     OR   c.service_type = 'XYZ')

     WHERE b.data_year_month = 199707

     ORDER BY 1;

This query returns 13,010 rows.