DB2 9 for z/OS Hints and Tips for Application Programmers

Index on Expression
V8
How to improve performance of
queries that include expressions
such as in the following examples:
SELECT id
FROM employee
WHERE
UPPER (lastname, 'EN_US') = 'JOE'
AND
UPPER (firstname, 'EN_US') = 'JOHN'
SELECT id
FROM employee
WHERE
bonus + salary > 100000
V9
Indexes on expressions:
CREATE INDEX upper_empname
ON employee
(UPPER (lastname, 'EN_US'),
UPPER (firstname, 'EN_US'))
CREATE INDEX total_compensation
ON employee
(salary + bonus)
• Extra cost in Load, Insert, Update on
key value, Rebuild Index, Check
Index, and Reorg Tablespace, but not
Reorg Index
• Not eligible for zIIP offload
• The rules for creating indexes on
expression are more restrictive than
for traditional indexes