And apart from the differences in cost on the simple test, you also remove the information about uniqueness and non-nullability if you don't declare the primary key, and this has an impact on the optimizer's decision tree.
Bear in mind, also, that Oracle will rarely do a tablescan on the inner table of a nested loop - so you may get a fifteen table hash join if you don't have any indexes, and this MIGHT go to one of the two possible extremes of demanding nearly 14 x hash_area_size in memory, or 14 allocations of temporary extents on your temporary tablespace. Regards Jonathan Lewis http://www.jlcomp.demon.co.uk Coming soon a new one-day tutorial: Cost Based Optimisation (see http://www.jlcomp.demon.co.uk/tutorial.html ) Next Seminar dates: (see http://www.jlcomp.demon.co.uk/seminar.html ) ____England______January 21/23 ____USA_(CA, TX)_August 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]> Date: 07 January 2003 02:45 > >There can be quite a difference between using >an index on a small table, and not using one. > -- 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).
