That sounds complex, maintaining different databases. Wouldn't it be better to just log all your dives in the same database, and then if you want to be able to sort out separate types of dives use metadata? Like a tag for a training dive or something? What do you do if some dives in the future that overlap categories - like if you have a fun dive in a lake, or a training dive at a resort? Obviously, this is just a conversation, we all do whatever we like with our logs, and if this works well for you, that's great. But I like having all of my dives accessible and searchable, and available to me everywhere (the MacDive log is synced with the app on my phone).
For example, I have three CCR tags: CCR_Training, CCR_Demo and CCR_JJ. If I were, for example, to buy a different rebreather someday, I would just add a tag for that. So now, when I want to see how many hours I have on the JJ outside of training, I just search for CCR_JJ, and the number appears in the bottom of the screen. If I wanted to see the total including training, then I would just search for CCR_Training and CCR_JJ. If I trained on another unit, I would make another tag for that and then just edit the tags so that the previous CCR_Training tags became CCR_Training_JJ, to keep it consistent...
Yes, that would be the 21st century way to do it, and the consistency of it does appeal to me. But my "databases" are paper. The vacation-diving log is the traditional compact 3-ring binder style with a format to record all the usual data, but especially marine life observations. The training log is a spiral notebook where most of the space is devoted to my stream-of-consciousness thoughts--the kind of thing a 21st century diver might keep a blog for. When I leave for a trip or a course, I take the corresponding log with me.
I gave electronic logging a try and did not like it. I deleted Subsurface from this computer yesterday to free up disk space. Maybe it was the very fact that, but for tags, all log entries "look" the same that did not appeal to me.