Yes, that is even a more narrowing detail. (people that use a "time-series" rarely need that high of granularity!) But the question was about wondering "why ex

Yes, that is even a more narrowing detail. (people that use a "time-series" rarely need that high of granularity!) But the question was about wondering "why exist the support for PK that are not integers/guis, like dates"?. To be able to model a lot of things for what in the past (before RDBMS) and today (for upstarts engines) you will be tempted to add another data store (that rarely is that necessary). I know by a fact that some times is because people not realize you DON'T need to constrain your db to things like "only integers pks!"! P.D: I work in the enterprise sector. Is fun when something is composed of a cluster of disparate things purely by misunderstanding you could have solved it with a simple db, well done. Contrary to belief, a lot of my customers, their largest databases are 1-10GB each. A rdbms can happily go much much larger than that, if you give them a little love...