SQL 累計在線時間聚合查詢：SUM(DATEDIFF) 替代逐條更新

同 30567，直接聚合：

SELECT SUM(DATEDIFF(MINUTE, lastlogin, lastlogout)) AS total_minutes
FROM TblCharinfoTimeLog
WHERE charid = '123';

若需持久化，定時任務更新彙總表。