Valg af MYSQL-kolonne betinget

Jeg tror, ​​du kan bruge case when then syntaks som nedenfor:

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

Alternativt:

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