There are great open-source SQL editors out there, but none of them ever really clicked for me. DataGrip was the one that gave me the feeling of productivity and control over my database workspace. But once my enterprise license got canceled, instead of picking a new one I decided to build myself an editor the way I always wanted it to be.
So qub was built with an emphasis on SQL centricity, the basics done well, and a clean interface I enjoy looking at all day.
During development, to keep the interface consistent and easier to build, I created a Qt/QML component library (including fonts, icons, and theming) called Mahina, which I also open-sourced. If you're building desktop apps with Qt, it might save you from reimplementing the same primitives from scratch.