可以将4个字段放在一起用作连接两个表的密钥吗？

I am trying to create a solution which allows pilots to swap a 1, 2, 3 or 4 day trip for another pilot's 1, 2, 3 or 4 day trip. I have 3 tables, Pilot, Have and Want. A pilot creates a Have which, for example, is a 2 day on 10/20 (October 20th). This pilot wants a 3 day starting on the 22. Another pilot has the 3 day and he wants something like the other pilot's 2 day. The tables looks like this;I am trying to create a solution which allows p