How to use /*+ INDEX */

Question

Hi friends,
Where can I find documentation for the usage of [*+ INDEX */] in SQL statement?
Thanks,
Peter

Answer 1

First_Rows
The FIRST_ROWS hint explicitly chooses the approach to optimize response time, that is, minimum resource usage to return the first row. Results will be returned as soon as they are identified.
This hint causes the optimizer to make these choices:
If an index scan is available, the optimizer may choose it over a full table scan.
If an index scan is available, the optimizer may choose a nested loops join over a sort-merge join whenever the associated table is the potential inner table of the nested loops.
If an index scan is made available by an ORDER BY clause, the optimizer may choose it to avoid a sort operation.
The optimizer ignores this hint in SELECT statement blocks that contain any of the following syntax:
set operators (UNION, INTERSECT, MINUS, UNION ALL)
GROUP BY clause
group functions
DISTINCT operator
These statements cannot be optimized for best response time because Oracle must retrieve all rows accessed by the statement before returning the first row. If you specify this hint in any of these statements, the optimizer optimizes for best throughput.
Syntax:
/*+ FIRST_ROWS */
Example:
SELECT /*+ FIRST_ROWS */ emplid, cc_descr, ccnxt_descr
FROM ps_dwad_c_dl_vw
WHERE emplid = '0895801'