MySQL -如何分组小时，以30分钟为间隔

I'd like to select records in 1 hour intervals, along with the highest and loest value in the hour interval. I can do this on the hour (eg, 1:00 am, 2:00 am, 3:00 am), but I'd like to offset it by specified minutes (eg, 1:30 am, 2:30 am, 3:30 am, or 1:50am, 2:50 am, 3:50 am). I don't want to group by half-hour (eg 1:00, 1:30, 2:00, 2:30) This is the SQL I have for 1 hour intervals:I'd like to select records in 1 hour intervals,