On Apr 16, 2012, at 10:37 PM, Puneet Kishor wrote: > Thanks for your wise words. I am not at all under any illusion that this is > going to be easy, but it is worthy of an honest try. Two reactions -- > > 1. Why is `:provided_date BETWEEN valid_from AND valid_to` better than > `created_on <= :provided_date`? The latter requires storing only a single > date value for every row. Although, after some studying of the Pg timetravel > docs, seems like they too use a start and stop date.
Although the end date is not strictly speaking necessary, and can be derived from a previous start date, it make the query more natural: "date between start and end", as opposed to some other peculiar oddities… It also allows to express deletion in one fell swoop: delete a record by closing its end date. > 2. Yes, most constraint mechanisms might be useless or difficult to > implement, but I do need a PK. Well, I suspect you need the equivalent of, say, a "business key". Something that uniquely identify a record *outside* of its versioning. But such an identifier is most likely not going to be a primary key, in the traditional relational constraint sense of it. _______________________________________________ sqlite-users mailing list [email protected] http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
