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