如何处理需要与SQLite中的多个id匹配的id？

I'm new to databases, so I'll start by showing what I would do if I was using a simple table in a csv file. Presently, I'm building a Shiny (R) app to keep track of people taking part in studies. The idea is to make sure no one is doing more than one study at the same time, and that enough time has passed between studies.I'm new to databases, so I'll start by showing