Cam "buruienos", nu-mi place (mai ales UNION):

SELECT
s.Customer,
s.[Week], s.[Month], s.[year], s.Sales, CASE WHEN b.blocked IS NULL THEN 0 ELSE b.blocked END AS blocked
FROM Sales s
LEFT OUTER JOIN Blocking b ON
s.Customer = b.Customer
AND
s.Week = b.Week
AND
s.[Month] = b.[Month]
AND
s.[year] = b.[year]
UNION
SELECT
b.Customer,
b.[Week], b.[Month], b.[year], CASE WHEN s.Sales IS NULL THEN 0 ELSE s.Sales END AS Sales, b.Blocked
FROM Blocking b LEFT OUTER JOIN Sales s ON
b.Customer = s.Customer
AND
b.Week = s.Week
AND
b.[Month] = s.[Month]
AND
b.[year] = s.[year]

Nu am mai lucrat de mult cu reporting services, nu stiu ce mai poate face. Poate faimosul "tablix" (?????).