Mark Eckeard (11/26/2013)

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Hard to say w/o your schema and sample data but would this work?

select (T1.HB-T2.HB) as CalcValue

from SampleResults T1

inner join SampleResults T2

on T1.SubjectNumber = T2.SubjectNumber

where T1.SampleType = 1

and T2.SampleType = 3

Mark