Adjust date column for change over time - sql

Question

This is an easy enough problem, but wondering if anyone can provide a more elegant solution.
I've got a table that consists of a date column (month end dates over time) and several value columns--say the price on a variety of stocks over time, one column for each stock. I'd like to calculate the change in value columns for each period represented in the date column (eg, a daily return from a table filled with prices).
My current plan is to join the table to itself and simply create a new column for the return as ret = b.price/a.price - 1. Code as follows:
select Date, Ret = (b.stock1/a.stock1 - 1)
from #temp a, #temp b
where datediff(day, a.Date,b.Date) between 25 and 35
order by a.Date
This works fine, BUT:
(1) I need to do this for, say, dozens of stocks--is there a good way to replicate the calculation without copying and pasting the return calculation and replacing 'stock1' with each other stock name?
(2) Is there a better way to do this join? I'm effectively doing a cross join at this point and only keeping entries that are adjacent (as defined by the datediff and range), but wondering if there's a better way to join a table like this to itself.
EDIT: Per request, data is in the form (my data has multiple price columns though):
Date Price
7/1/1996 349.22
7/31/1996 337.72
8/30/1996 343.70
9/30/1996 357.23
10/31/1996 364.07
11/29/1996 385.04
12/31/1996 383.68
And from that, I'd like to calculate return, to generate a table like this (again, with additional columns for the extra price columns that exist in the actual table):
Date Ret
7/31/1996 -0.03
8/30/1996 0.02
9/30/1996 0.04
10/31/1996 0.02
11/29/1996 0.06
12/31/1996 0.00

Answer 1

I would do the following. First, use the month and year to do the self join. I woudl recommend you take the year * 12 + the month number to get a unique value for each month and year combination. So, Jan of 2011 would have a value of (2011 * 12 + 1 = 24133) and December of 2010 would have a value of (2010 * 12 + 12 = 24132). This will allow you to accurately compare months without having to mess with rolling over from December to January. Next, you need to supply the calculations in the select clause. If you have the stock values in different columns then you will have to type them out as a.stock1-b.stock1, a.stock2-b.stock2, etc. The only way around that would be to massage the data to where there is only one stock value column and add a stockname column that would identify what stock that value is for.
Using the Month and Year for the self join, the following query should work:
select Date, Ret = (b.stock1/a.stock1 - 1)
from #temp a
inner join #temp b on (YEAR(a.Date) * 12) + MONTH(a.Date) = (YEAR(b.Date) * 12) + MONTH(b.Date) + 1
order by a.Date