Wie PIVOTiere ich über bis zu 49 Felder?

Ihre erste Abfrage kommt der am nächsten, außer dass Sie nicht jeden case eingeschlossen haben in die Gesamtfunktion. Außerdem scheint es, dass Sie einige Spalten in group by nicht benötigen Klausel:

select
    [Encounter Number], 
    Proc1 = max(CASE When [Encounter Proc Sequence] = '1' Then [Procedure Code (Enctr)] END),
    SvcDate1 = max(Case When [Encounter Proc Sequence] = '1' Then [Date of Service] END),
    Surgeon1 = max(CASE When [Encounter Proc Sequence] = '1' Then [Surgeon] END),
    Proc2 = max(CASE When [Encounter Proc Sequence] = '2' Then [Procedure Code (Enctr)] END),
    SvcDate2 = max(Case When [Encounter Proc Sequence] = '2' Then [Date of Service] END),
    Surgeon2 = max(CASE When [Encounter Proc Sequence] = '2' Then [Surgeon] END),
    Proc3 = max(CASE When [Encounter Proc Sequence] = '3' Then [Procedure Code (Enctr)] END),
    SvcDate3 = max(Case When [Encounter Proc Sequence] = '3' Then [Date of Service] END),
    Surgeon3 = max(CASE When [Encounter Proc Sequence] = '3' Then [Surgeon] END)
    --- etc.
from EncounterProc
where [Date of Service] between '20090101' and '20091231'
    and [Procedure Code (ENCTR)] is not null
group by [Encounter Number], [Encounter Proc Sequence]