Select SEC_TO_TIME(SUM(TIME_TO_SEC(timediff(timeOut, timeIn)))) AS totalhoursFROM volHours WHERe username = 'skolcz'
如果没有，那么也许：
Select SEC_TO_TIME(SELECT SUM(TIME_TO_SEC(timediff(timeOut, timeIn))) FROM volHours WHERe username = 'skolcz') as totalhours
