How can I find the Max/Min value in SQL Server as well as the time it occurred at? -

i have table being updated every 10 minutes data of flow rates, @ end of day need query generate average flow, minimum flow value , time occurred @ (same max) , total flow day. have far:

select * [ws6].[dbo].[masterdata] [_datetime] between '2015-07-06' , '2015-07-06 23:59:59' 

this gets me whole days data, how can filter values need? thank you

in sql server 2012, can use first_value():

select avg(flow), min(flow), max(flow), sum(flow),        first_value(_datetime) on (order flow asc) mintime,        first_value(_datetime) on (order flow desc) maxtime [ws6].[dbo].[masterdata] [_datetime] >= '2015-07-06' , [_datetime]  < '2015-07-07'; 

in earlier versions can use window functions or cross apply.