Articles & Content


F11 - How We Code SQL - Does It Matter?

Topic: Cross Platform DB2 for z/OS & LUW

Subtopic: 2015

This presentation would be based on application developer experiences with coding efficient SQL.

Introduction to basic concepts on how data can be accessed, what is Indexable , stage1, stage2, boolean term predicates.
There will be examples of re-writing queries according to few rules of thumb so it execute more efficiently,
What SQL to use, what trying to avoid, how you can influence access path with adding extra predicates, with special 'tricks', etc.

This joined presentation with IBM, will also mention how DB2 can do query rewrite for you. With focus on V10 and V11 query re-write possibility:
V10: How DB2 modifies IN predicates,
simplification of join operations,
removal of pre-evaluated predicates,
predicates that DB2 generates
and predicates generated through transitive closure

V11 - How DB2 11 simplify YEAR(col), DATE(col), and SUBSTR(col,1,len)
Simplify stage 2 BETWEEN predicate
Improve indexability of CASE expression predicate
Simplify always true or always false predicate
Enhance correlated to non-correlated subquery transformation
Predicate push-down enhancement

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