DATEDIFF(類型，開始時間，結束時間）
DATEADD(類型，時間間隔，時間)
CAST(數據 as 轉換類型)
DATEDIFF(HOUR,DATEADD( HOUR,sf.kaiShiShiJian_hour , CAST( sf.kaiShiShiJian_date AS DATETIME) ), DATEADD( HOUR,sf.jieShuShiJian_hour , CAST(sf.jieShuShiJian_date AS DATETIME) )) chiXvShiJian,