Also, reducing your problem down to a minimal reproducible example, along with some sample data (and ideally a http://sqlfiddle.com/ or https://dbfiddle.uk/ link) will get you much better answers. Source: about 1 year ago

Http://dbfiddle.uk has an AdventureWorks test DB that you could use. Source: about 1 year ago

If you used https://dbfiddle.uk to create a table, load it up with a minimum set of representative rows, then created a minimal, yet representative "first query" and then mocked up what you want your "second query"'s output to look like based on the example data, it might be way easier to comprehend what you are talking about. Source: over 1 year ago

Put it in a fiddle, like dbfiddle.uk or sqlfiddle.com. Source: over 1 year ago

I don't mean to take anything away from this post - its quite amazing and I can't wait to play with it more - but wanted to mention that there are sites out there that I believe solve the training portion maybe a little bit better, at least if all you want is to train on SQL not DBA type actions. My favorite is https://dbfiddle.uk/ - the ability to link and fork a set of statements is extremely handy. - Source: Hacker News / over 1 year ago

Check out Skyflow. They built a privacy vault to specifically address this issue. Source: over 1 year ago