Since "standard" users are not going to learn SQL your market is narrowed to developers only.
You may add a GUI based Query-Builder such as can be found in MS Acess and MSSqlServer and other DB systems and by these you can gain more market share.
Build an easy to use wizard and let the end user choose between SQL mode and GUI mode.
Power users aren't _that_ narrow a user base. There are an enormous number of data miners (analysts, integrators, etc.) out there who work in Excel because they must, or because they're used to it, or because that's the format that their data arrives in, or because it's a nice visual tool that allows them to easily inspect intermediate results---but who ultimately need to run reports across multiple large spreadsheets. SQL is astonishingly easy for such people, and I've watched dozens of data experts learn it from scratch (with help).
I'd beg you not to add wizards to your product, and instead focus on treating power users rather than being all things to all people. (Your syntax highlighting is good, and little red underlines on unparseable SQL would be good.) Trying to train users to use (or avoid using) SQL with wizards is a dangerous business for a piece of software to be in.
This looks incredibly useful. I'll check it out more thoroughly on Monday.
I can see the arguments both for and against wizards and gui query tools.
On the one hand I personally agree with the jcdreads and viggity. These sorts of interfaces are very difficult to get right and dilute the SQL focus.
On the other hand a number of people have suggested going this way, so people do think it would be useful.
I have no immediate plans to go this way but I intend to be responsive to what customers request.
Cheers