Index order in Oracle 10g

Question

Hi
I have a query:
I have a table having date and status as fields. Date is indexed.
Now i want to know whether the performance will hit if i make the query as:
where status = 'A' and date >= sysdate-100 and date <= sysdate
Does it matter that the where clause ordering should be as per ordering of indexes?
Similarly the same thing for partition. If date field is partitioned, will the partitioning advantage is there if we put status condition first.
Regards

Answer 1

The optimizer will choose the order of operations that it believes will cause your query to run the most quickly regardless of the order you specify conditions in your WHERE clause. The optimizer's decision will be driven by a number of factors-- optimizer parameters, database version, system statistics, table statistics, index statistics, histograms, the selectivity of your conditions, etc. No one can say with any level of certainty what the optimizer in your particular database with your particular tables and indexes with your particular statistics would generate for a query plan.
If you as a human have reason to believe that the date condition is sufficiently selective that the optimizer should use that to do an index range scan as the first step, the optimizer should come up with that plan assuming your statistics back up your intuition.
Justin