I have a table (trades) with some stock-trades

It has the following fields
id (autogenerate, key)
stock (int)
tradetime (datetime)
price (decimal (10,4))
stockcount (int)

Now it would like to make an SELECT from 'trades' that will give me
min (the smallest price value)
max (the largest price value)
open (the first price value, - i.e. the price for the trade with smallest tradetime and should there be more smallest id)
close (the last, - like open but opposite)

GROUP BY stock, LEFT(tradetime,10)
WHERE "some where clause that will select fewer dates and/or stocks, - I'll will vary (but generally include a stock = N and I don't think I'll get into troubles with this part)

MIN and MAX is quite simple
But how do I do open and close?