select sum (GRN1)
from (select SUM(t.CENA*z1.KOL_M1) as GRN1
from tovar t , zakaz01 z1
where t.GOD='2003' and t.KOD=z1.KOD

union all

select SUM(t.CENA*z2.KOL_M1) as GRN1
from tovar t , zakaz02 z2
where t.GOD='2003' and t.KOD=z2.KOD)

Ругается Token unknown - line 2, char 5.
А в Oracle проходит.