The K/Q people (http://kx.com/) have one interesting interpretation. It's quite expensive for production use* and uses an APL dialect as a query language, which tends to scare away a lot of developers. I'm utterly fascinated with it, albeit from a distance. (J is cool, too, but doesn't come bundled with a high-end in-memory database.)

* I've heard it can run $60k/CPU. It's designed for realtime stock data mining (https://cs1.cs.nyu.edu/cs/faculty/shasha/papers/hpts.pdf), so they get away with it.