I have a table that has three fields
EquipId I
ReadDate DT
Meter N10.1

What I need to do is calculate how many hours each EquipId changed in the last 30 days. ReadDate is the DateTime of the meter reading (this is taken weekly). Meter is the reading from the hour meter.

Do I need to do three selects? One to select the max readdate meter and one to select 30 days ago and one to figure out the difference??

I know that I can do a MAX(ReadDate) to get the max date... How do I select a ReadDate that is closest to 30 days? Do I need to step back until ReadDate is > 30 then select on that date? Just thinking out loud...

Thanks