求救，？这道题怎么解？

richto

Thank you for your response, I think most DB2 users may think DB2 optimizer's internal rewrite can solve every SQL problem, but if you have a deeper research in database optimizer, you will find that all database optimizer has its limitations.  Here the following is my paper for your reference, actually I got pay to write this paper and it is not a marketing materials.
http://www.ddj.com/documents/s=7119/ddj0205e/0205e.htm

DB2 internal rewrite cannot replace human rewrite (or external rewrite), something that only human can solve, DB2 and Oracle has their SQL optimization direction.  Oracle is more open to public to influence their optimizer, but DB2 is so self-driven.  So, once DB2 has SQL problem, it hard to tune by programmer, SQL Expert's AI engine is try to help user to solve their problem.  I am not a sale, but technically I am the expert in this field.  Even Sybase had OEM our product as their SQL tuning tool.  I am Hong Kong Chinese, but would like to bring some good products to our mother country - China.

clive

肯定是D
可以看到执行的步骤