Generally speaking, the round robin is also a competition similar to the competition system. For example, the Asian Cup, the predecessor of the AFC Champions League, was divided into the top four in East Asia and the top four in West Asia after the appearance of the top eight. For example, if a country is selected to hold a tournament, four teams will play in that country, that is, each team will only play against the opponents in the same group once, which is called a single round robin.
At present, it is still a single round robin, and it is a UEFA Cup group match with five teams in each group. Playing single round robin means that each team has only four games, in which each team can get two home games and two away games. This is reasonable. However, it depends on luck for each team to play against their opponents in two specific home games.
Generally speaking, single round robin is not common and is often used as a method to compress the schedule.