On Jun 1, 2018, at 10:16 , Olivier Gautherot <oliv...@gautherot.net> wrote: > > You will get a benefit in terms of space only if the optional fields in the > second table exist in a reduced number of instances - and the second table is > significantly wider. This can make a difference on big tables but this gain > may be offset by the cost of the join. In this perspective, I don’t think > that there is a clear benefit or drawback: it should be evaluated on a > case-by-case basis.
It seems to me that people take time to catch up with modern hardware reality. SSDs reduce seek time to virtually zero. Surely, joins are now much, much cheaper. If so, I’m inclined to describe wide tables as a premature optimization.
