I'll admit I haven't played with Copilot yet (since I don't think my employer would be happy for me to send off proprietary code to third-party servers, so I've effectively self-banned myself from using it at work*), but I'd feel that for anything non-trivial like your example of complex SQL queries I'd be reluctant to use the generated output without extra scrutiny (essentially a very fine-toothed code review, which is exhausting).
My opinion will probably change as the tools become more mature, but for now I'm treating them as toys primarily which limits the excitement.
Something like TLDR is less risky as it's not producing code, just summarising it, but I'd still feel wary to trust it since it's such a new field. Maybe this speaks more to my own paranoia than anything else!
EDIT: *and on this topic while I'm here: I'm actually a bit confused (and honestly... jealous?) on the topic of privacy for these kinds of external models. Is everyone who's using Copilot and tools like this working at non-Bigcos? Or just ignoring that it's sending off your source code to a third party server? Or am I missing something here?
It'd be against the rules to use external pastebins or other online tools that send off private source code to a server, so I'm kind of shocked how many devs are talking about how they use AI tools like this at work... is this just a case of "ask for forgiveness, not permission"?