There is a "uid" field in the "Competition", "Team", "Player" and "Coach" interfaces.

Because we may have duplicate data.

For example, "id:l965mkyh9wgr1ge" and "id:2y8m4zhgx28ql07" are the same player. But they have two different ids. We will merge these two data after we find them.

We make the data of "id:2y8m4zhgx28ql07" the correct data

Then the "uid" of "id:l965mkyh9wgr1ge" will be "2y8m4zhgx28ql07"

And the "uid" of "id:2y8m4zhgx28ql07" will be empty

（ps: Duplicate data may exist. We will conduct regular inspections and processing. Customers just need to keep the interface synchronized normally.）