Percentage difference between numbers in two fields

[natonstan]

My SQL experience is fairly minimal so please go easy on me here. I have a table named tblForEx and I'm trying to create a query that looks at one particular filed titled LastSalesRateChangeDate and also ForExRate.

Basically what I want to do is for the query to check that LastSalesRateChangeDate and then pull the ForExRate that is on the same line (Obviously in the ForExRate field), then I need to check to see if there is a +/- 5% change since the last time the LastSalesRateChangeDate changed. I hope this makes sense, I tried to explain it as clearly as possible.

 

[natonstan]

I've managed to get this code from someone, I can't work out why it won't work, am I right in thinking I need to replace the 't' with my table tblForEx?

select t.*, ( (t.ForExRate / tprev.ForExRate) - 1) as change_ratio
from (select t.*,
             (select top (1) t2.LastSalesRateChangeDate
              from tblForEx as t2
              where t2.BaseCur = t.BaseCur and t2.ForCur = t.ForCur
                    t2.LastSalesRateChangeDate < t.LastSalesRateChangeDate
              order by t2.LastSalesRateChangeDate desc
             ) as prev_LastSalesRateChangeDate
      from t
     ) as t inner join
     tblForEx as tprev
     on tprev.BaseCur = t.BaseCur and tprev.ForCur = t.ForCur
        tprev.LastSalesRateChangeDate = t.prev_LastSalesRateChangeDate;

 

[Micron]

CROSS POSTED HERE
Percentage Difference Between two fields?
nanostan - please read why this is not cool Excelguru Help Site - A message to forum cross posters

 

[xenou]

The t is okay, since it's part of the function. If it doesn't work, there's some other problem.