>

>SELECT *;
>  FROM a ;
>    JOIN b ON a.f1 = b.f1 ;
>    JOIN c ON b.f1 = c.f1
>

>
>Table a is joined with b.
>Table a is joined with c. Therefore, the part "on b.f1 = c.f1" is not appropriate.

Not so. Table a is joined with b. Then, that result is joined with c, so the condition shown is fine.

Tamar