** SQL tuning question

From: A Joshi <ajoshi977_at_yahoo.com>
Date: Mon, 1 Mar 2004 14:32:43 -0800 (PST)
Message-ID: <20040301223243.39018.qmail@web60710.mail.yahoo.com>

Hi,
I have a query joining three tables similar to the following :

select c.cust_name, o.order_number, ro1.related_order_number from order o, customer c, rel_orders ro1

where  c.cust_id = o.cust_id
and    c.cust_type = 'OV'
and    o.order_number = ro1.order_number
and    ro1.related_order_number in (select ro2.related_order_number from rel_orders ro2
                                   where  ro2.order_number = :v_order_number)

Tables order and customer are huge (millions) and rel_orders is very small (hundreads). I would like the optimizer to go to the small table first then get the order_number and go to orders table which has index on order_number and then go to cust table with cust_id(indexed). I tried the hint /*+ ordered (ro2 ro1 o c) */ but it does not help. I even tried to give the index hint for bigger tables but that does not help. it either does full table scan or index_full_scan. I tried several ways of writing the query but it does not help. I tried without the condition : and c.cust_type = 'OV'. No use. Please note that there can be more than one related_order_number for a order_number. Has someone encountered a similar case and can someone help. Thanks.

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Received on Mon Mar 01 2004 - 16:29:59 CST