I believe some do offer SQL-like query languages.

But if all you support is lookup by key, or even just lookup by field, then SQL really isn't that useful in my opinion. And if your lookups are based on map-reduces that have to be pre-specified then I can't see any place for an SQL-like language at all.

SQL is ok for specify queries to relational databases, but I don't think it generalises to any type of store apart from maybe the very basics. And at that point what benefit are you getting appart from a slight, and misleading, sense of familiarity?