Bob Badour wrote:
>"Lauri Pietarinen" <lauri.pietarinen@atbusiness.com> wrote in message
>news:3F94BCBB.7030001@atbusiness.com...
>
>
>>I could now denormalise OrderDetail so that it contains cust_id also
>>and cluster by cust_id
>>(might cause you trouble down the road, if you can change the customer
>>of an order), in which case, with 3 I/O's I would get
>>- 8 customer rows
>>- 16 order rows
>>- 24 order detail rows (which would all apply to one customer)
>>
>>
>
>Depending on block size, by clustering the three tables together, one might
>get all of those rows for a single read potentially improving on Wol's
>numbers by a factor of eight or more for this one query. Of course, doing so
>would increase the cost of a table scan on the customer table.
>
>
Which DBMS'es support clustering of mutiple tables except for Oracle?
Is this feature really used any more?
I thought it was more trouble than worth.
regards,
Lauri