Hi, yeah, I am okay with design prudence, just used to be so paranoid about performance that just any possible "one more thing to do" gets me nervous :) Language versions do exist, say Dutch has different orthography depending on what convention is used, so you may well need to suddenly add a further level of definition. But you can pretty much do that by a sequence of alter tables, especially in a situation like this.
Oh well, we are discussing principles as applied to a practical situation that we actually ignore, so... It's been a pleasure, but unless we get more detail... not much we can do apart from putting out personal preferences :) Bèrto On 24 July 2013 11:05, Luca Ferrari <fluca1...@infinito.it> wrote: > On Wed, Jul 24, 2013 at 11:47 AM, Bèrto ëd Sèra <berto.d.s...@gmail.com> > wrote: > > Hi, > > > > It looks heavy, performance-wise. If this is not OLTP intensive you can > > probably survive, but I'd still really be interested to know ow you can > end > > up having non unique records on a Cartesian product, where the PK is > defined > > by crossing the two defining tables. Unless you take your PK down there > is > > no way that can happen, and even if it does, a cartesian product defining > > how many languages a user speaks does not look like needing more than > > killing doubles. So what would be the rationale for investing process > into > > this? > > > You are probably right: you are like to never refactor this kind of > design, and this situation using a surrogate key is useless. But what > happens if your language is no more uniquely identified by > lpp_language_id? Suppose you need to track also the language version > and therefore a language is identified by the couple (id, version). In > this case you have to refactor two tables: the language one and the > person-language join table. > Having a surrogate key on both sides allows you to smoothly add such > constraint without having to refactor the latter table and ensuring > all previous joins still work. > Ok, not a really smart example, but the only one that comes into my > mind at the moment. > > Luca > -- ============================== If Pac-Man had affected us as kids, we'd all be running around in a darkened room munching pills and listening to repetitive music.
