The iPad has a massive touchscreen. I can think of several clever ways to visually 'build' queries by dragging-and-dropping query building blocks, column names, etc. into place.

Designing iPad apps around the idea of typing everything in is quite wasteful of that big touchscreen. Also, it doesn't give anyone a reason to purchase your app when they can just type the queries into their laptop/desktop with great efficiency.

Leveraging the touchscreen to turn a typing task into a visual, tactile task is a great use of the iPad.

Except that I use a bluetooth keyboard with my iPad...