Category Archives: data warehousing

Oracle OBIEE

Recently, I came across OBIEE. This is an Oracle tool that is created to support OLAP – type investigation into a database. I have to confess: I am impressed with it. The first great thing for me as an analyst is that it closely integrated into existing Oracle tool. One may continue to use the… Read More »


Sqoop is a tool that allows you to ship data from a RDBMS to a Hadoop platform. Let us take an example to clarify this. One may have some data in a MySQL table persons, within database thom. This database is stored on server The data can be accessed with the knowledge of the… Read More »

Avro – getting it work

When you read about Hadoop, you come across AVRO. This is a mechanism to exchange data via streams and it is named after the famous British aircraft industry that amongst many other types, delivered the Lancaster that helped to liberate Europe. AVRO can be implemented in many languages, amongst them PHP. Before continuing let us… Read More »

Map and reduce – what happens?

In Big Data, the concept of mapping and reducing plays a huge role. The idea is that a a massive dataset is split over several servers. On each server, a part of the data is investigated. This part is called a mapper. In a subsequent part, these parts are merged into an outcome. This latter… Read More »

Use Case

A Use Case is something that can be written after a context diagramme is written. A context diagramme provides an overview of the whole system with its interfaces to the outside world. The use cases are written on base of each of the individual interactions between the system an one of its external systems. As… Read More »

Requirements analysis

Recently I read a very interesting book on requirements analysis “Mastering the Requirements Process: Getting Requirements Right” by Suzanne Robertson and James Robertson. They wrote a practical book that lead to a template for such a document They advocate to spend enough time on requirements analysis, which can be described shortly as “getting to know… Read More »

Context diagrammes – understanding a scope

I came accross a very nice technique that can be used to show the scope of a project. It is called the Context Diagramme. The idea is that the system is shown as one item. The internal structure within the system is not displayed. Instead the diagramme shows the interaction from the system with external… Read More »

Yet another checklist

I often come across checklists. Such checklists are used to assess the quality of, say, a database. See here for an example of such a checklist. In this case, we have a checklist that is created to assess the quality of a Teradata database. Such checklist are very interesting. They are generally based on a… Read More »


I currently work in an organisation that has a debate on whether to use MOLAP or ROLAP. But first of all: what is discussed here? ROLAP and MOLAP are two different techniques to store data that are meant for OLAP analysis. In ROLAP the data are stored in tables in a relational database and each… Read More »

The Teradata answer on materialised views

Teradata has a feature that is designed to increase the performance of queries. This feature is called the “join index”. Such a join index is a structure that stores the outcomes from a query. These outcomes are stored permanently and they wait for the moment when they are called. The syntax of such a join… Read More »