Seems you need to combine data based on
period
,
year
and
source/destination
SELECT t1.Period AS Prd, t1.Year AS Year1, t1.Srce AS Src1, t1.Amt AS SourceAmount, t1.Desttination AS Dest1,
t2.Amt - t1.Amt AS Variance, t2.Srce As Src2, t2.Destination AS Dest2, t2.Period, t2.Year AS Year2, t2.Amd AS Amount
FROM YourTable AS t1
INNER JOIN YourTable As t2 ON
t1.Period = t2.Period AND
t1.Year = t2.Year AND
t1.Srce = t2.Destination AND
t1.Key < t2.Key
More about joins:
Visual Representation of SQL Joins[
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