[ErwinSmout]

That's because the true foundation is that relational algebra is (a) an algebra and (b) closed over relations. (a) means you should have an expressions system that allows arbitrary nesting and (b) means you should be able to arbitrarily nest relational expressions in particular. SQL fails heavily on (b) (it fails less so than it used to do with the SQL:1992 standard but even so, it's still far from where we should have been and SQL itself is still an abomination).

Moreover, your very examples illustrate how "thinking SQL" is *NOT* the path to finding proper solutions. .skip() and .take() clearly originate from the world of ranking problems and it drips off of every word that you were thinking of finding a "modern" way to specify [things like] "TOP 10", but those solutions are themselves a fundamentally crippled way to attack the problem.