ActiveRecord diff?


I have a situation where I would like to get the difference of the
last 2 records in each column in my DB.

So, lets say I have col1 and col2, with values below.

col1 = 1, 2
col2 = 3, 4

What I would like to do is iterate through each column name (col1,
col2) and get the difference of the last 2 records in each. Since it
doesn't look like there is a .diff command for active record, I'd like
to just store them in a variable and take the difference manually.

I have tried this, but it doesn't work, what am I doing wrong here?

# Give me the last 2 rows from col1?

result = Object.find(:all,:limit => 2, :select col1, :order =>
'enterdate DESC')
diffof_rows = result[0] - result[1]


And I guess the real question is, with the code below, should this
retireve the last 2 records in the table (I think I should use ASC)?