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Home » Monthly archive

January 2012

Should SQL have a compulsory ORDER BY clause?

Submitted by oraclebase on Fri, 2012-01-06 12:37

How many times have you heard someone say, “The rows always came back in the correct order, but since the *event* it’s now wrong. The *event* may be an upgrade or some maintenance task on the table etc.

Oracle clearly say,

“Use the ORDER BY clause to order rows returned by the statement. Without an ORDER BY clause, no guarantee exists that the same query executed more than once will retrieve rows in the same order.”

This also applies for the GROUP BY clause, that haunted people during their 10g upgrades.

“The GROUP BY clause groups rows but does not guarantee the order of the result set. To order the groupings, use the ORDER BY clause.”

Both these statements can be found in the docs for the SELECT statements.

The Most Brilliant Science Graphic I Have Ever Seen

Submitted by mwidlake on Thu, 2012-01-05 19:57

The below link takes you to an absolutely fantastic interactive demonstration of the relative size of everything. Everything. Stop reading this and go look at it, when it finishes loading, move the blue blob at the bottom of the screen left and right.

The Relative_scale_of_everything

The raw web link is:

http://www.primaxstudio.com/stuff/scale_of_universe/scale-of-universe-v1...

The web page says scale_of_the_universe but it should be relative_scale_of_everything_in_the_universe. Did you go look at it? NO!?! If it’s because you have seen it before then fair enough – otherwise stop reading this stupid blog and Look At It! NOW! GO ON!!!

Yes, I do think it is good.

Happy (belated) New Year!

Submitted by tkyte on Thu, 2012-01-05 16:39

Another year, another list of 'resolutions'.  Welcome to twenty-twelve :)

Adding Datafiles

Submitted by Niall Litchfield on Thu, 2012-01-05 16:30

Yesterday I talked about some of the things to consider when adding space to a tablespace using auto-extend for datafiles. This of course isn’t the only way to add space to a tablespace. You could simply add more datafiles. Indeed nearly a decade ago (scary!) I wrote The final reason for multiple datafiles (to spread [...]

Life is nonlinear

Media: 
See video

Part 2 of Cary Millsap's UKOUG 2011 keynote, "Learning about Life through Business and Software." Life is nonlinear.

Submitted by cary.millsap on Thu, 2012-01-05 15:43

Thinking clearly is more important than the right answer

Media: 
See video

Part 1 of Cary Millsap's UKOUG 2011 keynote, "Learning about Life through Business and Software." Thinking clearly is more important than the right answer.

Submitted by cary.millsap on Thu, 2012-01-05 15:36

Mission: Impossible – Ghost Protocol

Submitted by oraclebase on Thu, 2012-01-05 15:03

Mission: Impossible – Ghost Protocol is OK for a Tom Cruise action vehicle. It is more or less the same as all the others in the franchise, which is not a bad thing. It just doesn’t bring anything new to the table. I knew it would be like this which is why it took me some time to work myself up to seeing it.

If you like the others go to see it. If you have not been won over to the franchise yet, I don’t think this one will do it. :)

Cheers

Tim…

Curious Case Of The Ever Increasing Index Solution (A Big Hurt)

Submitted by Richard Foote on Thu, 2012-01-05 05:37

Based on the excellent comments in the Quiz post, we have some clever cookies out there I guess the first thing to point out is that based in the basic scenario provided, the index shouldn’t ordinarily be continually growing in this fashion. Although the index values are monotonically increasing, the deletions are leaving behind fully emptied leaf blocks which [...]

Index size bug

Submitted by Jonathan Lewis on Wed, 2012-01-04 18:29

Here’s a follow-up to a post I did some time ago about estimating the size of an index before you create it. The note describes dbms_stats.create_index_cost() procedure, and how it depends on the results of a call to explain plan. A recent question on the OTN database forum highlighted a bug in explain plan, however, which I can demonstrate very easily. I’ll start with a small amount of data to demonstrate the basic content that is used to calculate the index cost.

Product Review

Submitted by Niall Litchfield on Wed, 2012-01-04 18:15

I have got a offer from uCertify to review their Exam PrepKit. The terms of this were simply that I write an unbiased review (and you can be assured that no money is changing hands) so now I am reviewing Oracle 1Z0-052 PrepKit from uCertify which is the DBA 11G OCP Kit. I expect to [...]