On Fri, Jun 1, 2018 at 12:52 PM, Guyren Howe <guy...@gmail.com> wrote:
> It’s come to my attention that what seems an obvious and useful database > design pattern — 1:1 relations between tables by having a shared primary > key — is hardly discussed or used. > > It would seem to be a very simple pattern, and useful to avoid storing > nulls or for groups of fields that tend to be used together. > > Thoughts? Is there some downside I can’t see? > 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. Olivier Gautherot
