× The internal search function is temporarily non-functional. The current search engine is no longer viable and we are researching alternatives.
As a stop gap measure, we are using Google's custom search engine service.
If you know of an easy to use, open source, search engine ... please contact support@midrange.com.


  1.  Home
  2. MIDRANGE-L
  3. September 2005

Re: SQL efficiency vs. OPNQRYF

OPNQRYF & SQL, in one way of thinking, are just different interfaces to the query engine of the database on iSeries. There are now (since v5r2, at least) 2 paths, and SQL can sometimes take the newer one, with potential benefit for complex joins of certain types. There are several things that determine whether the new engine is used - there is an info APAR for that, go to www.iseries.ibm.com/db2 and dig around to get more info.
There are ways to optimize either OPNQRYF or SQL - a valuable tool is to run STRDBG with no program and then run the statement you are testing. There will be several statements that say what the optimizer did. Some will say that an index was built. Pay attention to the recommended index columns, create such an index, and see whether the performance improves. The same index will help both OPNQRYF and SQL - it might even solve you old problems.
The join order can make a difference, as well, and there are some settings that can force certain things using SQL, just as there are with OPNQRYF.
Long answer, sorry. Short answer, it depends. With no new indexes, it is possible you will have the same problem. Maybe show us the commands and statements and let us take a shot at adjusting them. 

Cheers
Vern

At 05:50 PM 9/13/2005, you wrote:
Does anybody have any sort of educated opinion on relative efficiency of SQL vs. OPNQRYF, when doing complex (and mostly joined) queries on physical files?
In the project I'm working on that involves taking a rather Rube Goldberg contrivance of OPNQRYF calls, and re-implementing it in SQL, part of the complexity of the old OPNQRYF implementation was that with a complex query involving 2 levels of AND and OR across a bunch of files, trying to do it in a single OPNQRYF would take far longer (order of FOREVER) than breaking it down into a bunch of simpler OPNQRYFs. Am I likely to encounter the same problem with SQL? 

--
JHHL
--

As an Amazon Associate we earn from qualifying purchases.

This thread ...
Replies:
Follow On AppleNews
Return to Archive home page | Return to MIDRANGE.COM home page

This mailing list archive is Copyright 1997-2024 by midrange.com and David Gibbs as a compilation work. Use of the archive is restricted to research of a business or technical nature. Any other uses are prohibited. Full details are available on our policy page. If you have questions about this, please contact [javascript protected email address].

Operating expenses for this site are earned using the Amazon Associate program and Google Adsense.