SQL Agreate Functions

Hi,

I have a problem I dont really know how to solve except for writing a
function.

I have a table with prices;

SecCode| Price   | PriceDate
-------+------------+-----------
A0001  | 13.10   | 2004-10-30
A0001  | 13.03   | 2004-10-29
A0001  | 13.12   | 2004-10-28
A0001  | 12.45   | 2004-10-27
A0001  | 12.65   | 2004-10-26
A0001  | 12.45   | 2004-10-25

A0002  | 10.10   | 2004-10-30
A0002  | 10.45   | 2004-10-27
A0002  | 10.65   | 2004-10-26
A0002  | 10.45   | 2004-10-25
etc.

What I would like to calculate is:

a) the difference of the past 2 days for every security of
   available prices

b) a flag indicating, that the price of today-1 is yesterday's
   price (true in case A0001, false for A0002)

c) the variance of the past 30 days


Is it possible to do that within one query?

Thanks for any advise
Alex