There is also noria [0] which is basically a SQL database with integrated materialized views with memcached like perf. - But I think it is more in a research state.
The work in general purpose streaming grew out of the continuous query work in the early 2000s. Marrying truly general purpose streaming with transactional databases is not a solved problem (as opposed to transactional databases providing streams), but the notion of continuously running database queries has been around for a long time.