When working with the Clustering algorithms, and particularly k-Means, in the Oracle Data Miner tool there is no way of seeing how compact or dispersed the data is within a cluster.
There are a number of measures typically used in various tools and algorithms, but with Oracle Data Miner we are not presented with any of this information.
But if we flip from using the Oracle Data Miner tool to using SQL we can get (more...)
It helps you to easily jump between different functions/procedures inside a package.
My colleague Holger told me about a bug in SQL Developer 3.x where you could use the "Outline" view with normal SQL files, too. Unfortunately in version 4 it didn't work anymore. So he stayed with version 3 for a long while. Otherwise he would had to (more...)
I think Tom Kyte was the originator of this technique. It's not necessarily the fastest method, but it's super convenient - no table required.
Today I wanted to know how many weekdays a year, so I defined 365 rows on the fly using sysdate to turn these into each day of the year. Then I ran a simple (more...)
Die Select-Statements in diesem Blogpost habe ich von anderen Webseiten kopiert. Daher ist dieser Beitrag eher als Zusammenfassung unterschiedlicher Lösungsversuche zu sehen und dient mir als schnelle Hilfe bei der Verkleinerung eines zu großen Tablespaces. Schaut euch die Quellen an, die sehr viel detaillierter auf die jeweiligen Probleme eingehen.
Wer kennt nicht die Situation? Der DBA ruft an und meint der TEMP Tablespace verbraucht mehrere hundert Gigabyte an Speicher.
Was ist in solch einer (more...)
This week I was in an excellent presentation by Kerry Osborne about Outlines, SQL profiles, SQL patches and SQL Baselines. I’ve used three of those features in anger but when I looked at SQL Patches I just could not understand why you would use them – they looked to me like a very limited version of SQL Profiles.
So I asked Kerry about it (more...)
If you are a user of the Oracle Data Miner tool (the workflow data mining tool that is part of SQL Developer), then you will have noticed that for many of the algorithms you can specify a Case Id attribute along with, say, the target attribute.
The idea is that you have one attribute that is a unique identifier for each case record. This may or may not be the case in your data model (more...)
Distinguish Real Execution Plans from Fake Ones!
As an Oracle DBA, one of our daily tasks is to optimize bad SQL statements that are affecting the system and causing performance degradation. First we identify the culprit SQL, then we extract the execution plan, after that, we start the cycle of SQL tuning and optimization as appropriate.
There are many methods to extract the execution plan for a specific SQL statement, however, not all these (more...)
We have gone through a merger at our company where we are trying to merge the databases. The problem now is that we have duplicate records in our tables. We can of course go through all the records by hand and check if they exist twice. Another option is to build an application to do this. But using the Oracle Database there must be a better way to do this. Any ideas?
This is my contribution to the OTN Appreciation Day, which was initiated by Tim Hall.
One of my favorite features of the Oracle Database are Analytic Functions. They were introduced with Oracle Database 8.1.6 Enterprise Edition, and have been in the Standard Edition since version 9.
With analytic functions you can add inter-row calculations, aggegrate over multiple dimensions, rank assignments based on values. All this without a GROUP BY clause.
The syntax might (more...)
Oracle 12c introduced the ability to specify sequence.nextval as the default on a column, which is really nice – including the fact that it eliminates one of your excuses why you don’t decommission those old triggers.
Unfortunately it doesn’t work as you might expect if you use an
INSERT ALL statement; it evaluates the default expression once per statement, instead of once per row.
create sequence test_seq; create table test_tab ( id number default (more...)