SQL: Update mit Select und IF/CASE in der Bedingung

[dataspider]

Reicht da nicht ein OR?

SQL-Code:

update
  ADR
set
  Value = (select SUM(B.Brutto) as Summe from BEL B
             where
               (B.Art = 'BLUBB' or B.Art = 'BLA') and
               ( (B.Adr > '' and B.Adr = ADR.Adr) or
                 (B.KDNR = ADR.Adr)
               )