Path: news.easynews.com!newsfeed1.easynews.com!easynews.com!easynews!newsfeed.news2me.com!arclight.uoregon.edu!logbridge.uoregon.edu!news-west.eli.net!not-for-mail Message-ID: <3DA5C68D.56CFE5F2@exesolutions.com> From: Daniel Morgan X-Mailer: Mozilla 4.79 [en] (Windows NT 5.0; U) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: comp.databases.oracle.server Subject: Re: 1=1 References: <91884734.0210091256.32c7fe4b@posting.google.com> <91884734.0210100915.3b64eb81@posting.google.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 32 Date: Thu, 10 Oct 2002 18:28:00 GMT NNTP-Posting-Host: 156.74.250.7 X-Complaints-To: yvonne.tracy@ci.seattle.wa.us X-Trace: news-west.eli.net 1034274480 156.74.250.7 (Thu, 10 Oct 2002 12:28:00 MDT) NNTP-Posting-Date: Thu, 10 Oct 2002 12:28:00 MDT Organization: City of Seattle NewsReader Service Xref: newsfeed1.easynews.com comp.databases.oracle.server:163763 X-Received-Date: Thu, 10 Oct 2002 11:27:56 MST (news.easynews.com) Karsten Farell wrote: > Joel Garry wrote: > > I was hoping that wouldn't be the answer. But... it's the _last_ > > one... > > [and I've seen others ending with AND 1=1) AND 1=1)] > > > > I just have some vague memory from years ago that it had some sort > > of useful effect in rule-based. > > > > jg > Maybe the 1=1 on the end is tacked on as a result of not selecting > anything from a drop-down list on the UI (as the value of the default > item). I suspect the cost-based optimizer throws away the 1=1 clauses > anyhow (no matter where they are). > > You might be remembering the old tricks we used on the rule-based > optimizer (did it really optimize anything?) to avoid index usage - eg, > select column+0 or column||''. Perhaps they still work with CBO (unless > it has grown so smart it knows when to ignore us). There are times when using 1=1 makes a significant difference in the execution plan selected by the CBO. And thus, it can dramatically improve performance of a query. As to why? I can't say. But I had a query once where dragging DUAL into it provided the same improvement. Go figure. Not doubt Howard, Jonathan, Tom, and other can. I can't. Daniel Morgan