Example 1: Outer Join That Is Really an Inner Join - Teradata Database

Example 1 makes an explicit outer join request, but its result might surprise you.

     SELECT c.custnum, b.monthly_revenue

     FROM sampdb.customer AS c

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

     WHERE c.district ='K'

     AND   b.data_date = 199707

     AND  (c.service_type = 'ABC'

     OR    c.service_type = 'XYZ')

     ORDER BY 1;

This query returns 13,010 rows, the same as the simple inner join of “Inner Join Cardinality Estimate” on page 266.