The biggest problem with hints is that you cannot specify a full set - in particular there is no effective way to handling unnesting of subqueries.
For simple cases, you can put the tables in the main query in the 'correct' order and use the ORDERED hint, then name the indexes and join mechanisms you want. But if you have any subqueries things break if Oracle unnests, so you need to hint the subqueries with NO_UNNEST. On the other hand, unnesting may be desirable, in which case you have to rewrite the query in an unnested form, otherwise the unnested tables go to the top of the FROM list, and the ORDERED hint applies incorrectly. There is no easy option until you get to v10 - where a couple of hint enhancements make it much simpler to specify your requirements. Regards Jonathan Lewis http://www.jlcomp.demon.co.uk The educated person is not the person who can answer the questions, but the person who can question the answers -- T. Schick Jr One-day tutorials: http://www.jlcomp.demon.co.uk/tutorial.html Three-day seminar: see http://www.jlcomp.demon.co.uk/seminar.html ____UK___November The Co-operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html ----- Original Message ----- To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]> Sent: Tuesday, December 02, 2003 8:44 AM > Hi, > > my question is about the same, but more general. How can i force Oracle to use my prefered way of explain plan and not use CBO's. I mean, apart from stored outlines, it somehow seems to complicated. I would like to say what order and join types it should use. But, try as I might, I many times cannot force Oracle to use my way, even though I know it is possible, for I saw this kind of explain plan for that specific query.. > > I tried to use hints like ordered and use_hj etc. Can someone give some examples of full set of hints for some simple queries? > > Thx, > rw -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Jonathan Lewis INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
