In my previous blog post I introduced the new Explicit Semantic Analysis (ESA) algorithm and gave an example of how you can build an ESA model and use it. Check out this link for that blog post.
In this blog post I will show you how you can manually create an ESA model. The reason that I'm showing you this way is that the workflow (in ODMr and it's scheduler) may not be for everyone. (more...)
Have you seen ROWNUM and ROW_NUMBER in Oracle and wondered what the difference is? Learn what they are and the differences between Oracle ROWNUM vs Oracle ROW_NUMBER in this article. What Is Oracle ROWNUM? You might think that ROWNUM is a function in Oracle. However, it’s not a function. It’s a “pseudocolumn”. It acts like […]
In this article, I’ll be covering the Oracle TO_MULTI_BYTE function, and look at some examples. Purpose of the Oracle TO_MULTI_BYTE Function The TO_MULTI_BYTE function is used to convert a character string from single-byte characters to multi-byte characters. Your database must contain both single-byte and multi-byte characters for this function to be useful. If there are […]
In this article, I’ll explain what the COVAR_POP function does and show you some examples. Purpose of the Oracle COVAR_POP Function The Oracle COVAR_POP function calculates the population covariance of a set of number pairs. What is a “population covariance”? Good question. Here’s an article that explains what the definition is. Just like the COVAR_SAMP […]
I explain what a primary key and foreign key is, as well as the differences between primary key vs foreign key in this article. What Is a Primary Key? What is the primary key definition? A primary key is one or more columns in a table that are used to uniquely identify the row. When […]
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Whilst I was working on the functional specification for the LISTAGG extensions that we implemented in 12c Release 2, I came across Tom Kyte’s stragg function which uses the User Defined Aggregate API introduced in database 9i. Tom’s comprehensive answer... [Read More
It’s always a challenge when you want to build your own Oracle SQL Tools. I was asked how you could synchronize multiple cursors into a single source. The answer is quite simple, you write an Oracle object type to represent a record structure, an Oracle list of the record structure, and a stored function to return the list of the record structure.
For this example, you create the following
table_struct object type and a
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Doesn’t matter who much testing you do (well, it actually does but that’s a whole different issue) you can almost guarantee that at some point your beautiful data validation code, that parses data input from a web form or loads data from some external file, will pop up with... [Read More
A new Oracle Data Mining algorithm in the Oracle 12.2c Database is called Explicit Semantic Analysis.
[The following examples are built using Oracle Data Miner 4.2 (SQL Developer 4.2) and the Oracle 12.2 Database cloud service (extreme edition) ]
The Explicit Semantic Analysis algorithm is an unsupervised algorithm used for feature extraction. ESA does not discover latent features but instead uses explicit features based on an existing knowledge base. There (more...)
The last version of Oracle in which CHOOSE was officially supported as an OPTIMIZER_MODE parameter value was 9.2.
This is what the documentation of Oracle 9.2 says about it:
The optimizer chooses between a cost-based approach and a rule-based approach based on whether statistics are available.
If the data dictionary contains statistics for at least one of the accessed tables, then the optimizer uses a cost-based approach and optimizes with a goal (more...)
While visiting a customer, we had a conversation about the correct way to stop users from writing to code tables. The customer described his ancient logic: when he wanted to move table to a read only state, he removed the write (insert/update/delete) permissions from all of his users. That was good enough for him for years – since he started using this method way back in Oracle 8. All was well, util this week he (more...)
When inserting data into the database, it is occasionally forgotten (especially by English-speakers) that we need to take steps to ensure we are inserting data correctly and without unexpected character translation.
For example, in SQL*Plus we need to ensure we set the NLS_LANG environment variable to the correct setting for our database before we initiate SQL*Plus.
Here’s a quick example showing what can go wrong:
[oracle@ORA122 ~]$ echo $NLS_LANG
[oracle@ORA122 ~]$ sqlplus neil/neil
SQL*Plus: Release (more...)
The internet is full of information about indexes, and for a reason. Indexes in a database is probably the most important performance related topic. There are so many cases, properties, and different ways to use indexes that there is simply a lot to write about. In this post I’d like to talk about a specific … Continue reading Scanning an Index
In a previous blog post I talked about how you can rename and comment your Oracle Data Mining models. This is to allow you to easily to see and understand the intended use of the data mining model.
Another feature available to you is to audit the usage of the the data mining models. As your data mining environment grows to many 10s or more typically 100s of models, you will need to have some (more...)
Suppose that every time we add records into the T1 table we have to do some additional stuff.
One option to implement this is by using an AFTER INSERT trigger that will perform this additional stuff, but I really dislike this option (mainly because the code becomes hidden in a way, and there may be a negative impact on performance).
I prefer writing a procedure that inserts the records into T1 and performs this additional (more...)
As your company evolves with their data mining projects, the number of models produced and in use in production will increase dramatically.
Care needs to be taken when it comes to managing these. This includes using meaningful names, adding descriptions of what the model is about or for, and being able to track their usage, etc.
I will look at tracking the usage of the models in another blog post, but the following gives examples (more...)
I presented this topic on at Tech 16 on Monday afternoon. The latest version is on the Tech 16 website and on http://www.slideshare.net/StewAshton1/ranges-ranges-everywhere-oracle-sql Thanks to the organisers, staff, presenters and delegates who made this a great conference and a wonderful experience!
I presented this topic on Super Sunday. The latest version is now on the Tech16 site and on http://www.slideshare.net/StewAshton1/advanced-row-pattern-matching
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...)
Most of you probably know the "Quick Outline" function you have inside the SQL Developer.
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...)