Find centralized, trusted content and collaborate around the technologies you use most.
Teams
Q&A for work
Connect and share knowledge within a single location that is structured and easy to search.
关系 R: [A,B,C,D,E,F] FD1: (A,B) - C,F FD2: (C,D) - E FD3: (D,E) - B
(x,y) 是这里的候选键吗?如果不是,那是什么?