Ini mungkin berhasil:
SELECT a.ProductID, Hash1, Hash2
FROM (select ProductID, BINARY_CHECKSUM(*) AS Hash1 from TableA a) a
JOIN (select ProductID, BINARY_CHECKSUM(*) AS Hash1 from TableB b) b on ...
Masalah Anda hanyalah masalah sintaksis. Pendekatan Anda akan berhasil.