Question: I added an index hint in my query, but
the hint is being ignored. What is the correct syntax for an index hint
and how do I force the index hint to be used in my
query?
Answer: Oracle index hint
syntax is tricky because of the index hint syntax is incorrect it is treated as
a comment and not implemented. Here is an example of the correct syntax
for an index hint:
select /*+ index(customer
cust_primary_key_idx) */ * from customer;
Also note that of you alias the table, you must use the
alias in the index hint:
select /*+ index(c
cust_primary_key_idx) */ * from customer c;
Also, be vary of issuing hints that conflict with an
index hint. In this index hint example, the full hint is not consistent
with an index hint:
select /*+ full(c)
index(c cust_primary_key_idx) */ * from customer c;
Oracle index hint syntax,布布扣,bubuko.com
原文：http://www.cnblogs.com/reynold-lei/p/3574643.html