I'm not sure if you saw my update with a "piece of paper" from a crime scene analogy?
I used the Url as the link between tables because it was easily available and guaranteed unique.
So why have 2 tables?
Answer: I didn't want to set or declare a maximum number of columns in the main ScoreCard table.
Each entry in the ScoreCard table can have an unlimited number of Participants.
Why use integer id instead of Url?
Answer: because it would save space. I didn't do it or need to do it in this case.
Could a situation arise where a human shouldn't be required to enter a unique field for a row and where number of columns is not fixed?
Answer:Absolutely.