Oracle Database 12c: Interactive Quick Reference

12c DB Architecture

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Interview question: second largest value

This is my first blog for a very very long time.  I stopped blogging a couple of years ago when I started working on my book and after I finally finished the book I felt I needed a break to recuperate.

However, I have finally decided to put my toe back in the water.  This isn’t a very serious post but I hope you find it thought provoking and a bit of fun.


INDEX FULL SCAN (MIN/MAX) und partitionierte Tabellen

Eine Frage, die ich mir gelegentlich schon einmal gestellt hatte, und dachte, die Antwort hier im Blog bereits notiert zu haben, lautet: ist der INDEX FULL SCAN (MIN/MAX) als Zugriffsoption auch für partitionierte Tabellen möglich? Da diese Antwort aber auf Anhieb unauffindbar zu sein scheint und womöglich von mir nie protokolliert worden ist, schreibe ich sie (noch einmal?) auf:

drop table t;
create table t
( id number
, startdate date
partition by range (more...)

MATCH_RECOGNIZE: matching based on aggregates

The heart of row pattern matching is finding which row matches what part of the pattern. Within the 12c MATCH_RECOGNIZE clause, DEFINE lists the conditions a row may meet; it doesn't always work the way you expect, especially if you use aggregates in the condition.

Washington memorials

I'm no patriot, and I'm certainly not American.

I'm somewhat of a pacifist, but I appreciate the efforts of the brave in years past. I certainly felt an urge to to shake the hands of some of the aging veterans we saw as we passed the WWII memorial.

What moved me most, however, was walking through the Lincoln memorial.

There was some amazing prose on those walls. Considered words, unbiased by the various media of (more...)


Boston is a nice city, smaller than expected but full of culture.

The weather was great for us and we took one of the Duck tours which took off from right outside our hotel.
From out piggy tumblr
We don't get much in the way of American history in Australian schools, and most of what I know comes from movies or general interest. We had an amazing character driving our duck, a fella named Tim (more...)

The Hills were Alive with the Sounds of #DataVault

Yes folks a few weeks back we held the 2nd Annual World Wide Data Vault Consortium (#WWDVC) at the lovely Trapp Family Lodge outside Stowe, Vermont. What a great venue! Beautiful scenery, near perfect weather, great food, and great beer (they have their own brewery). Standing on the hillside it is easy to see why […]

Mac SQL Developer Install

This how you install SQL Developer on Mac OS Yosemite. The first thing you need to do is download and install Java 8, not Java 7 on your Mac OS Yosemite, as suggested on some web sites. You can determine whether or not Java is installed by running the following command:

Mac-Pro-3:~ username$ java -version
No Java runtime present, requesting install.

You must accept the Java license to install Java 8 on the (more...)

Kscope Journey

Boy that was a long trip.

Sure, Perth to Dubai was 11 hours but on a brand new half full Airbus it wasn't so bad, even if we didn't get in early to move away from the bulk head seats. The leg room was handy while bubba was awake, but arm rests that don't fold up made it harder to get her to sleep.

I think though the most boring part was the 3 hour (more...)

Deadlock with a Virtual Column

Virtual Columns are really cool. I like them a lot. If you've never heard of them, shame on you, learn about them.
In short: a Virtual Column is not a real column, it's an expression that looks like a column... more or less.
While using the Virtual Columns, we ran into a little oddity with them.

First of all let's start with the version of the database that I tested this on. Yes, I know (more...)

Feasibility survey of a possible European Kscope-like conference

As most people likely to read this blog will know, I am a great fan of the ODTUG Kscope yearly conference for Oracle developers. In my opinion it is one of the absolute best places for awesome content, presenters, attendees and networking - all wrapped in one high quality package that's fun too.

Some Dutch developers (Erik van Roon, Gert Poel and more) and I had a little twitter discussion some time ago. (more...)

MP Oracle Blog 2015-06-10 23:34:00

Mauro Pagano zeigt in seinem jüngsten Artikel einen Fall, in dem ein Bloom-Filter in den Filter-Prädikaten eines Execution Plans erscheint, aber im Plan selbst nicht aufgeführt wird. Seine Analyse zeigt, dass es sich dabei um ein Problem der Darstellung in dbms_xplan handelt: in 11.2 fehlt der Filter, aber in 12.1 wird er korrekt angezeigt. Interessant ist dabei vor allem die Analysestrategie: zunächst bestimmt er mit Hilfe von Event 10128, dass ein weiterer im (more...)

Merging Overlapping Date Ranges with MATCH_RECOGNIZE

I forgot to add a MATCH_RECOGNIZE solution to my last post on merging overlapping date ranges! That should take me just a few minutes, right? Wrong: it’s not that easy and here’s why. For test data, please refer to the previous post. To Merge or not to Merge? The idea is to merge date ranges if […]

Run X11 Apps on Mac

It’s possible folks didn’t notice but Mac OS X no longer includes XQuartz by default from Maverick forward. You need to download XQuartz and install it. I’d recommend after you install Xcode.

Launch XQuartz and then either use the bash shell it opens or open a Terminal bash shell session. Inside the shell, you might start Secure Shell (ssh) like this:

Mac-Pro-3:~ michaelmclaughlin$ ssh student@
student@'s password: 

Fedora X11 Install

While working through getting my Mac OS X to work with X11, I stumbled on some interesting errors and misdirection solutions. Like most things, the solution was straightforward. Then, it struck me that I hadn’t installed it on my Fedora image. This blog post show you the errors I got the way to get it to work, and how to install X11 on Fedora.

The first step requires discovering the package. If you remember xclock (more...)

Installing Oracle XE, ORDS and Apex on CentOS – Part One: Preparation

This is part one in a series of blog posts about how to install Oracle 11g Express Edition (XE) with Oracle Application Express (Apex) on a CentOS Linux server, with Apex served by Oracle REST Data Services (ORDS) running on top of Tomcat and Apache.

Provisioning the server

First of all, we need a server to install the software on. There are many hosting providers that offer cheap Linux servers. I have been trying out (more...)

Merge für überlappende Intervalle

Ein Thema, das in SQL regelmäßig viel Freude bereitet, ist die Logik der Verschmelzung von Intervallen. Da ist es sehr nützlich, wenn sich jemand wie Stew Ashton der Fragestellung annimmt, den Tom Kyte in seinen Oracle-Magazin-Artikeln schon wiederholt anerkennend erwähnt hat. In seinem aktuellen Artikel Merging Overlapping Date Ranges stellt der Autor zunächst die 13 möglichen Fälle der Intervall Agebra von James Allen vor und liefert dann eine überraschend kompakte SQL-Lösung dazu (die letztlich eine (more...)

In case you wish to download Apex 5.0 documentation as a zip file

For some reason the official page for Oracle Application Express release 5.0 doesn't include a download link for its documentation library, while archived releases are all available for download from the following page: Fortunately for us the consistency in Oracle's internal documentation library organization

Merging Overlapping Date Ranges

A recent question on the OTN forum asked about merging date ranges. Thanks to Karthick_App I realized that my previous blog on this subject was incomplete. Here is a solution that will merge any date ranges that meet, or that "overlap" in any way.

Installing Oracle XE, ORDS and Apex on CentOS

I am writing a series of blog posts about how to install Oracle 11g Express Edition (XE) with Oracle Application Express (Apex) on a CentOS Linux server, with Apex served by Oracle REST Data Services (ORDS) running on top of Tomcat and Apache.

This is perhaps better explained with an illustration of the setup:

Best of all, this setup consists only of free (license-free) software, and as you will see in this series of blog (more...)