Force optimizer to use hash/nl/merge join?

Hi All,

Is there any way to force the optimizer to use a specific join operator?
For example, in SQL Server, I can do this way

select * from (A inner hash join B on A.a = B.b) inner loop join C on A.a =
C.c

I did some search but didn't find PostgreSQL had similar join hints except
for enable_* setting which doesn't help in my case.

Best Regards,
Zhan