How to force a Index?

Question

HI, i know that using the hint /*+ index(NOMBRE_TABLA NOMBRE_INDICE) */ it force to use an index specified.
but is another way to do this?
i hear that doing this it work too, and in the explain plan looks good but does't retrieve data.
example
select a.field1
from table1 a, table2 b
where a.fieldkey1 = b.fieldkey1
and -a.fieldkey2 = b.fieldkey2
index1 = a.fieldkey1
index2 = a.fieldkey2
look the minus sign in the index 2
can someone help me about this?
Thanks, sorry by my english

Answer 1

Intentional index supression usually occurs with the rule-based optimizer, when the RBO chose to use an index but not the one you wanted or perhaps to force a full table scan for some reason. Its not widely used these days. Modifying a column value should suppress index use; the way its usually done is to add 0 to numbers/dates or concatenate a null to strings leaving the actual value unchanged. IF you need to do this (and I'm wondering why you do) document your code some Those Who Come After don't see strange code and immediately change it on sight
select *
  from whatever
where number_column + 0 = whatever
   or string_column || null = whatever