getPhotos: excluding those already played before by the player

SELECT a.imageId, a.imageUrl, 1 as confidence, 1 as bool_prediction,
answer FROM XImage as a LEFT JOIN XPlay as b ON a.imageId = b.imageId
WHERE answer = ? AND (b.keyId is NULL OR b.playerId != ?)
$cond_answer_confience_for_beginner $order LIMIT ?