MySQL查询从小时至2小时

Question

如何更改下面的查询获得2小时，而不是1

SELECT DATE_FORMAT(x.time,'%Y-%m-%d %H:00:00') 
    , avg(Ph) avg_Ph 
    FROM Ph x where time >= NOW() - INTERVAL 1 DAY 
GROUP 
    BY DATE_FORMAT(x.time,'%Y-%m-%d %H:00:00'); 

Answer 1

SELECT DATE_FORMAT(FROM_UNIXTIME(FLOOR(UNIX_TIMESTAMP(x.time)/7200)*7200),'%Y-%m-%d %H:00:00') AS `two_hour` 
    , avg(Ph) avg_Ph 
    FROM Ph x where time >= NOW() - INTERVAL 1 DAY 
GROUP 
    BY `two_hour`