Syntax for raw Druid queries?

Hi, Could you please tell me what kind of syntax is expected when writing druid queries ?
SQL does not seem to work…

We don’t currently support raw druid queries. We have an issue open - https://github.com/metabase/metabase/issues/2072

If this is something you’re looking to use heavily, could you chime in on that issue to give us a sense for what the queries would be expressing that can’t be expressed in the query builder?