Jak odróżnić te same nazwy pól dwóch tabel w zapytaniu wybierającym?

Po prostu napisz tak,

select a.field1 as af1,a.field2 as af2,a.field3 as af3,b.field1 as bf1,b.field2 as bf2,b.field3 as bf3,c.field1 as cf1,c.field2 as cf2,c.field3 as cf3 from table A as a, table B as b,table C as c where so and so.