Data, data en nog eens data

Author: tom

  • The overextended usage of surrogate keys

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    tom
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    I recently encountered a situation whereby surrogate keys were used as primary keys. It looks as a reasonable choice; since the so-called SCD2 mechanism was also used to store historic information. The mechanism then works as follows: if we get updated information on a record that is already in the table, we insert a new…

  • Mainframes

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    About hundred years ago, I worked on a mainframe. I those days, the mainframe was basically the mainstream computer that many people used. In those days, financial institutions started automating their business processes. In the nowadays world, these mainframes are still the workhorses of these financial institutions. But how did we access them? Now, I…

  • Accessing Oracle from Perl

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    This weekend had bad weather. Rain pouring from the sky and a drop of snow. Such weather is good to undertake something that is absolutely useless like writing a Perl programme on Linux to access a remote Oracle database. The first hurdle to overcome is to install an Oracle client along with some Perl routines…

  • Layers in Visio

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    tom
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    Sorry to say, but I love Microsoft Visio. Plse do not spread the word. But from time to time, I had to create a document that served two distinct groups: a group who was just interested in getting a highlight and a group who wanted to go into details. In earlier times, I created two…

  • Add blobs in your database

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    tom
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    For some reason, I always overlooked the possibility to include pictures in a database. I decided to overcome this flaw and started experimenting with it. The first step was to create a table in Access. In Access, we have the possibility to use the datatype “OLE Object”. A field with this datatype can be used…

  • Use bteqwin as a Teradata client

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    I installed teradata recently. The installation was really straight forward. And as a bonus, you get tons of client tools. It is possible to use several clients to start your sql. A popular tool is BTEQWIN. However, if you google on BTEQWIN, you get lots of questions that ask: how do I connect to the…

  • Installing Oracle – the host is localhost!

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    tom
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    Yesterday, I started installing Oracle. I decided to download the newest version: version 11g R. I used windows xp as a platform with DHCP switched off. It really looked simple: the screens look simple and the questions asked were straight forward. I let it go for about 2 hours and after this time I returned…

  • Free ETL tool

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    Yesterday evening, I received a copy of Expressor. This is a free ETL tool which made a very good impression to me. I downloaded the copy from http://www.expressor-software.com . The download and subsequent installation is very simple. The file to be downloaded is about a 100MB and the installation is straightforward: some legal screens and…

  • Ranking the rows

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    tom
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    I was asked a few days to write a SQL that would retrieve the one but latest row. Take as an example a few rows below: we have a several functions with their min salary. The question is: which function earns the one but highest minumum salary. In the rows below, we have minimum salary…

  • SQLite

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    tom
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    SQLite is the smallest database server we know. The engine itsself is about 500 KB – considerably less than other engines. It can be downloaded from http://www.sqlite.org/ . Once downloaded, it can be started by: sqlite3 test.db. Here, the sqlite3 is the database engine that is called and test.db the database. I have downloaded a…