mysql计算两个时间的小时数

例子:
SELECT p.*,
sum(round((TIMESTAMPDIFF(SECOND ,DATE_FORMAT(p.starttime,'%Y-%m-%d %H:%i:%s'), DATE_FORMAT(p.endtime,'%Y-%m-%d %H:%i:%s')))/3600,2 )) hh

FROM 表名 p WHERE (p.date BETWEEN '2016-12-01' AND '2016-12-31') AND p.status in (0,6) GROUP BY userid
HAVING hh<167