On Saturday, 14 October, 2017 04:37, Richard Damon <rich...@damon-family.org>, wrote:
>One way to make them build one to at-most-one relationships is too >add a unique index on the foreign key, then it can only occur once. >A True one-one relationship by the normailization rules says that >they should all be in the same record. Only for lower levels of normalization. At the higher normalization levels optional 1:1 related data, particularly any which contains meaningful relations between the candidates and data of that relation of its own, goes into its own relation joined to the parent through a 1:1 relationship. It can also be viewed as a physical layer implementation optimization where no such requirement exists from normalization to move the optional relation into its own 1:1 relation. Of course, if you normalize all the way up to where you end up with a "virtual master" containing only relationships to the actual data containing relations, then this will always be in a 1:1 relation with the master. _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
