There are a lot of semi "power users" with little CS background that write simple SQL queries for their work.

I think the main difference is in the level of curiosity/caring the person exhibits when they get a result you don't expect. When they do something that they think should work and it doesn't, do they carefully figure out the system behind it and why?

The users that do will write better queries faster, and the others will will just keep getting frustrated and foist the work onto others.