Get Tags specific to Category

I've noticed there is no native way to retrieve tags based on the category. I've seen a few plugins that do something similar but don't this.

There have also been been a few snippets posted that kinda do it but either show duplicates of tags, or seem too labor intensive.

In short has anyone done a db query as follows:

select category
from category select posts
from posts select post tags
make array of unique post tags (id, name, slug)

I've started playing with the query function but as I'm learning and shooting in dark.

Any help, even a quick tut on how to run a query would be helpful.