Need To Know Why Two Calculation Methods Result In Different Rounding Effect

Hi All,

I have a view that does some calculations on data in the database. Note in the two code snippets, that the columns being used in the calculations are all type FLOAT(53).

My confusion stems from the fact that both code snippets should be functionally the same in my "view" (*snicker* I kill me...), but they return different results which I think are related to rounding issues.

The first snippet:

CREATE VIEW dbo.VIEW_Calculate_PortfolioIndex
AS
SELECT PP.PortfolioID AS PortfolioID,
PP.CreateDate AS CreateDate,
(ROUND((PPI.CloseIndex + (PPI.CloseIndex * PP.DailyPerChg / 100.00)), 2) * PP.AvgHighPriceRatio) AS HighIndex,
CASE WHEN PPI.CloseIndex IS NULL
THEN 100.00
ELSE ROUND((PPI.CloseIndex + (PPI.CloseIndex * PP.DailyPerChg / 100.00)), 2)
END AS CloseIndex,
(ROUND((PPI.CloseIndex + (PPI.CloseIndex * PP.DailyPerChg / 100.00)), 2) * PP.AvgLowPriceRatio) AS LowIndex,
PP.Volume as Volume
FROM dbo.PortfolioIndex PPI INNER JOIN
dbo.PortfolioPerformance PP ON
PPI.PortfolioID = PP.PortfolioID AND
PPI.CreateDate = PP.PrevDate
GO

and it's result set:
PortfolioIDCreateDateHighIndexCloseIndexLowIndexVolume
102/20/2004781.11774.17769.53527896
112/20/2004757.97750.36742.93605740
122/20/2004509.92501.72494.854180516
132/20/2004988.23980.65973.58632337
142/20/20041283.261269.571259.37416145


And the second snippet:

CREATE VIEW dbo.VIEW_Calculate_PortfolioIndex
AS
SELECT PP.PortfolioID AS PortfolioID,
PP.CreateDate AS CreateDate,
(CloseIndex * PP.AvgHighPriceRatio) AS HighIndex,
CASE WHEN PPI.CloseIndex IS NULL
THEN 100.00
ELSE ROUND((PPI.CloseIndex + (PPI.CloseIndex * PP.DailyPerChg / 100.00)), 2)
END AS CloseIndex,
(CloseIndex * PP.AvgLowPriceRatio) AS LowIndex,
PP.Volume as Volume
FROM dbo.PortfolioIndex PPI INNER JOIN
dbo.PortfolioPerformance PP ON
PPI.PortfolioID = PP.PortfolioID AND
PPI.CreateDate = PP.PrevDate

which returns a different result set:
PortfolioIDCreateDateHighIndexCloseIndexLowIndexVolume
102/20/2004784.52774.17772.89527896
112/20/2004755.64750.36740.64605740
122/20/2004512.43501.72497.294180516
132/20/2004989.77980.65975.1632337
142/20/20041285.991269.571262.05416145


Specifically, I am concerned with the HighIndex and LowIndex values...since the only modification between the two code snippets is that in the second one, the HighIndex and LowIndex calculations use the column name of CloseIndex (as calculated in the select) in the calcs for those two columns, rather than repeating the code used to calculate the CloseIndex column's value.

I am confused as to why the results of the HighIndex and LowIndex caculations are different in the two selects, when the only change (in my view/expectations) is that one references the CloseIndex column, and the other one just reproduces the calculation itself

*scratching head*

any thoughts? Thanks,
Paul