From oracle-l-bounce@freelists.org Fri Feb 20 17:35:02 2004 Return-Path: Received: from air189.startdedicated.com (root@localhost) by orafaq.com (8.11.6/8.11.6) with ESMTP id i1KNZ2727387 for ; Fri, 20 Feb 2004 17:35:02 -0600 X-ClientAddr: 206.53.239.180 Received: from turing.freelists.org (freelists-180.iquest.net [206.53.239.180]) by air189.startdedicated.com (8.11.6/8.11.6) with ESMTP id i1KNYwo27374 for ; Fri, 20 Feb 2004 17:34:59 -0600 Received: from turing (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 7F69E39774E; Fri, 20 Feb 2004 18:07:04 -0500 (EST) Received: with ECARTIS (v1.0.0; list oracle-l); Fri, 20 Feb 2004 18:06:02 -0500 (EST) X-Original-To: oracle-l@freelists.org Delivered-To: oracle-l@freelists.org Received: from mail.acelerate.com (mail.acelerate.com [200.105.128.132]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with SMTP id 74F293952EB for ; Fri, 20 Feb 2004 17:20:51 -0500 (EST) Received: (qmail 28769 invoked from network); 20 Feb 2004 21:51:32 -0000 Received: from dazasoftware.com (HELO org48l7d9ara8b) (200.105.151.94) by 0 with SMTP; 20 Feb 2004 21:51:32 -0000 Message-ID: <001501c3f7ff$a3c87390$2501a8c0@dazasoftware.com> From: "Juan Cachito Reyes Pacheco" To: References: Subject: Re: What I'm doing? explanation about my posts Date: Fri, 20 Feb 2004 18:19:42 -0400 MIME-Version: 1.0 Content-type: text/plain; charset=Windows-1252 Content-Transfer-Encoding: 8bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1158 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 X-archive-position: 1520 X-ecartis-version: Ecartis v1.0.0 Sender: oracle-l-bounce@freelists.org Errors-To: oracle-l-bounce@freelists.org X-original-sender: jreyes@dazasoftware.com Precedence: normal Reply-To: oracle-l@freelists.org X-list: oracle-l Yes sorry, the second one select is out of this explanation It should be SQL> select count(*) from daz.utl_tablas_me where tbl_dsm is null; COUNT(*) --------- 359 To demonstrate there is nulls :=) ----- Original Message ----- From: To: Sent: Friday, February 20, 2004 5:06 PM Subject: Re: What I'm doing? explanation about my posts Juan, Your goal of providing informative articles is laudable. You might want to consider the following 2 queries more closely. SQL> select count(*) from daz.utl_tablas_me 2 where tbl_dsm in 3 (select null from daz.utl_tablas_me); COUNT(*) --------- 0 This query proves that an arbitrary column is never equal to null. SQL> select count(*) from daz.utl_tablas_me 2 where exists(select null from daz.utl_tablas_me); COUNT(*) --------- 310 This query also proves that an arbitrary column is never equal to null, and in addition, proves that there are 310 rows in the utl_tablas_me table. It doesn't tell you anything about the value of any column in the utl_tablas_me table, including whether or not any of the columns are null. >From the examples it is unclear what you are trying to prove. Maybe you just need different examples? Jared "Juan Cachito Reyes Pacheco" Sent by: oracle-l-bounce@freelists.org 02/20/2004 11:43 AM Please respond to oracle-l To: cc: Subject: What I'm doing? explanation about my posts Hi, I like to write articles, at the same time I investigate something I share it to other so it could be useful, I did one Tom Kyte check (about flashback) but he didn't have more time. I ask Burleston if he would have time, because I saw he likes some communitary activities, but he neither ansewr my email. What I'm doing now is posting interesting topics, principally brief, for every one, I am including in an article about basic tuning (bulk collection, null in in() ) I soonly will put in my page on geocities, so based on the feedback to improve, The idea is a very simple explanation and introduction, but enough clear, so if you want more information you go to tahiti.oracle.com, search and get a copmlete answer. for example I improved in() explanation When comparing any value using IN with NULL values, IN don't return TRUE hence, ignore null values as you can see in the table there are 310 null values in column TBL_DSM. SQL> select count(*) from daz.utl_tablas_me 2 where tbl_dsm in 3 (select null from daz.utl_tablas_me); COUNT(*) --------- 0 SQL> select count(*) from daz.utl_tablas_me 2 where exists(select null from daz.utl_tablas_me); COUNT(*) --------- 310 A more clear example of this situation you can see in this way select count(*) from dual where null in (null ); COUNT(*) --------- 0 bulkcollection to ... During execution, every SQL statement causes a context switch between the two engines. Performance can be improved reducing the number of contexts switches using FORALL for bulk collection to one. If you don't like you can simply ignore this posts :) Happy Carnaval ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@freelists.org put 'unsubscribe' in the subject line. -- Archives are at http://www.freelists.org/archives/oracle-l/ FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html ----------------------------------------------------------------- ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@freelists.org put 'unsubscribe' in the subject line. -- Archives are at http://www.freelists.org/archives/oracle-l/ FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html ----------------------------------------------------------------- ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@freelists.org put 'unsubscribe' in the subject line. -- Archives are at http://www.freelists.org/archives/oracle-l/ FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html -----------------------------------------------------------------