MYSQL-kolom voorwaardelijk selecteren

Ik denk dat je case when then . mag gebruiken syntaxis zoals hieronder:

SELECT CASE WHEN player1id = 1 THEN player2id ELSE player1id  END
FROM players WHERE player1id =1 OR player2id=1;

Alternatief:

SELECT CASE WHEN player1id = 1 THEN player2id WHEN player2id =1 THEN player1id  END
FROM players WHERE player1id =1 OR player2id=1;