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May 2013

Everything or Nothing in SQL

May 23, 2013 The following question recently came through an ERP mailing list (significantly rephrased): I would like to use the Microsoft Query tool in Microsoft Excel to extract records from the ERP database.  I would like the list of parent records to be retrieved into Excel when all of the specified child records belong to […]

Everything or Nothing in SQL

May 23, 2013 The following question recently came through an ERP mailing list (significantly rephrased): I would like to use the Microsoft Query tool in Microsoft Excel to extract records from the ERP database.  I would like the list of parent records to be retrieved into Excel when all of the specified child records belong to […]

Vague and/or misleading claims can undermine otherwise useful themes

I’m pretty much a green sneaker, tree hugging conservationist. (The Nature Conservancy, Audubon, and Arbor Day get annual renewals like clockwork, I helped write and implement Scenic Road and Wetlands Preservation legislation here in Lebanon, NH in the late 1980s.) So I’m really disappointed when loss of species and habitat headlines and statistics are so oriented to shock value that my reaction is “Is there a seed of truth in this obvious attempt to mislead?” instead of concern for the subject matter. Today’s entry for my #please_read_tufte hall of shame: “…facing 50 percent drops in their numbers within seven years if the current rate of decline continues…” I’ll save you the math: that’s about 9.43 % per year.

Dynamic Sampling – 2

I’ve written about dynamic sampling in the past, but here’s a little wrinkle that’s easy to miss. How do you get the optimizer to work out the correct cardinality for a query like (the table creation statement follows the query):

select	count(*)
from	t1
where	n1 = n2
;

create table t1
as
with generator as (
	select	--+ materialize
		rownum id
	from dual
	connect by
		level <= 1e4
)
select
	mod(rownum, 1000)	n1,
	mod(rownum, 1000)	n2
from
	generator	v1,
	generator	v2
where
	rownum <= 1e6 ; 

If you’re running 11g and can changed the code there are a couple of easy options – adding a virtual column, or applying extended stats and then modifying the SQL accordingly would be appropriate.

Laptop and Desktop SSD Update…

I recently wrote about installing SSDs in my Laptop and Desktop. I thought I would write a quick follow up post to mention how things are going.

I’m really happy with the changes to the performance of the desktop. As mentioned previously, it is now much quieter and really fast. A lot of my VMs run from the 1TB internal data drive, but the things I use most frequently are now sitting on the SSD. I’m starting to forget what life was like before SSD, except when I go to work and use the slowest PC that was ever built. :)

gather_plan_statistics – 2

Some time ago – actually a few years ago – I wrote a note about the hint /*+ gather_plan_statistics */ making some informal comments about the implementation and relevant hidden parameters. I’ve recently discovered a couple of notes from Alexander Anokhin describing the feature in far more detail and describing some of the misleading side effects of the implementaiton. There are two parts (so far): part 1 and part 2.

 

Oracle Exadata Database Machine: Proving 160 Xeon E7 Cores Are As “Slow” As 128 Xeon E5 Cores?

Reading Data Sheets
If you are in a position of influence affecting technology adoption in your enterprise you likely spend a lot of time reading data sheets from vendors.  This is just a quick blog entry about something I simply haven’t taken the time to cover even though the topic at hand has always be a “problem.” Well, at least since the release of the Oracle Exadata Database Machine X2-8.

Oracle Exadata Database Machine: Proving 160 Xeon E7 Cores Are As “Slow” As 128 Xeon E5 Cores?

Reading Data Sheets
If you are in a position of influence affecting technology adoption in your enterprise you likely spend a lot of time reading data sheets from vendors.  This is just a quick blog entry about something I simply haven’t taken the time to cover even though the topic at hand has always be a “problem.” Well, at least since the release of the Oracle Exadata Database Machine X2-8.

I’m speaking at Enkitec Extreme Exadata Expo E4

Just a short notice to those interested that I’m very proud to be in the lineup for Enkitec’s Extreme Exadata Expo. The event takes place August 5-6, 2013 and is held in the Four Seasons Resort & Spa, Irving, Texas. There is plenty of time for you to register.

I was really sorry I missed out last year but this time I’m glad to participate and attend!

official site

The list of great speakers includes too many to name here-you should see for yourself about who is coming to Dallas this August and why this event is unmissable.

I’m hoping to see you there!