SQL as a stream processing language.
It is frustrating that SQL continues to exist, but I believe that despite funky syntax and bad semantics, it covers an important subset of language expressivity. It is a useful subset, and acts as a common culture for programmers to build new systems and explain it to other programmers without having to start from first principles. (Which lets you skip over some of the inevitable tide of negativity you face every time you try to introduce a new idea in programming.)
Anyway, PipelineDB looks really interesting.docs.pipelinedb.com/continuous-views.html