Overhead. By defining every column a a primary key, you are basically creating an index of the entire table. So any column that gets updated, forces the index to update. Hence making the indexes pretty worthless.
-Adam On Tue, 9 Nov 2004 09:42:31 -0500, Tangorre, Michael <[EMAIL PROTECTED]> wrote: > > From: Gavin Brook [mailto:[EMAIL PROTECTED] > > > > Personally I use an individual primary key myself. In the > > past I have seen oracle databases with two fields as the > > primary key, but never a whole record. The only justification > > I can see for having the whole record as the primary key is > > to save space. Adding an extra column to store a primary key > > requires the space to store it and the storage for the > > sequence. On modern servers storage is not usually a problem, > > particularly with such a small field. On older mainframes, it was. > > I can not speak to AS400 as that was the technology in text books 10 > years prior my college experience (yes I'm a youngin'). Anyway, any > space you "might" save will be lost when you do updates or selects in > which you want a specific record assuming there is a comparable stored > procedure concept on AS400. Consider the extra lines needed to determine > which record to update or select: > > UPDATE .... SET .... WHERE a=1, b=2, c=3, e=4, f=5 etc etc etc. > SELECT .... FROM .. WHERE a=1, b=2, c=3, e=4, f=5 etc etc etc. > > Compared to > > UPDATE .... SET .... WHERE a=1 > SELECT .... FROM .. WHERE a=1 > > That's not to say that there is never a need for compound keys comprised > of 2 or 3 columns such as those found in join tables, etc... > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| Special thanks to the CF Community Suite Gold Sponsor - CFHosting.net http://www.cfhosting.net Message: http://www.houseoffusion.com/lists.cfm/link=i:4:183728 Archives: http://www.houseoffusion.com/cf_lists/threads.cfm/4 Subscription: http://www.houseoffusion.com/lists.cfm/link=s:4 Unsubscribe: http://www.houseoffusion.com/cf_lists/unsubscribe.cfm?user=89.70.4 Donations & Support: http://www.houseoffusion.com/tiny.cfm/54
