This looks really cool, can't wait to check it out. The problem I've seen with other tools I've tinkered with is that they do well with simple stuff like:

"what are my latest orders" -> select * from orders where user_id=x order by created_date

But really struggle when you have a complex schema that requires joins, and basically has no support when you are describing something that needs outer joins or the like. Would be great to hear if DataHerald has cracked that nut or if it's still a challenge for you as well (no judgement if it is, it seems like a hard problem).