SELECT
comment.*,
COALESCE(users.avatarInGames, usersCache.avatarInGames) AS avatarInGames,
COALESCE(users.gameId, usersCache.gameId) AS gameId
FROM comment
LEFT JOIN users ON comment.UID = users.userId
LEFT JOIN usersCache ON comment.UID = usersCache.userId
WHERE comment.status = 1
ORDER BY comment.OID DESC;