MySQL's return value should have no impact on Derby, it's if Derby supports these features only.
Also, please be careful looking at MySQL code, bringing MySQL GPL code into Derby's codebase would not be acceptable.
Obviously in this case a return true/false is not an issue, but demonstrated access to a piece of work is enough for copyright infringements.
E.g. if someone says I looked at MySQL code to see how X was done and then implemented the same functionality in Derby in a similar manner that could be enough to pollute the Derby code base with GPL.