Find rows with identical columns by SQL


This is an article about how find rows in a table with one or more identical columns by SQL. The use case is to find entries in an account table with the same email address or with the same first name and surname. The trick is to join the table to itself.

Find all rows with the same email address:

SELECT left.*
FROM account left
INNER JOIN account right ON =
AND !=;

Find all rows with the same first name and the same surname:

SELECT left.*
FROM account left
INNER JOIN account right ON left.firstname = right.firstname
AND !=;

Deploy a Spring Boot Application to Pivotal Web Services


Spring Boot makes it easy to create stand-alone applications based on the Spring framework. Pivotal is the company behind the Spring framework. Pivotal is also running a cloud platform  called Pivotal Web Services (PWS). PWS provides a run time environment for several types of server based applications and PWS are particularly suitable for Spring Boot applications. If you are looking for a way to run your Spring Boot application „in the cloud“ take a look  at PWS. In this article I will show how to deploy a simple Spring Boot application in the  PWS environment.


Neo4j and JGraphT – A Perfect Team


Neo4j is an open-source graph database, implemented in Java. JGraphT is a free Java graph library that provides mathematical graph-theory objects and algorithms. JGraphT is a well fitting data model for Neo4j query results as well as it provides a rich pool of algorithms to process it. This article is about how to get a JGraphT graph object as a result from a Neo4j Cypher query. In order to reach this goal, I started the project jgrapht-neo4j-client.


Query Neo4j with Cypher using the REST API


Neo4j REST API provides a way to query the database with Cypher. Cypher is a declarative graph query language. See the Neo4j manual to learn more about it. In this article I will show how to use the REST API to execute Cypher queries from Java code.


A REST web service, file uploads & Spring Boot

In this article I will introduce a document archive application with a REST interface created with Spring Boot. You will find out how to handle file uploads by a REST web service. The web front end is created with AngularJS. The application is on GitHub. The impatient of you can follow this link to the repository: rest-document-archive to see the source code.


Berlin 2003, Ostgut, Restrealität



Vor 10 Jahren (2003) hat das Ostgut geschlossen. Hier ist der letzte, der schönste und der wichtigste Flyer aus diesem Club: „Restrealität“.


Applet Animation – Part One: Display

Applet "Display" (screenshot)

The applet  you see in the screenshot I coded a long time ago. Applets are dead. I know. But this one is too nice to rest in peace.  Weiterlesen

Berlin 1997, E-Werk


Ein Dubmission-Flyer aus dem E-Werk.

Das E-Werk in der Wilhelmstraße 43 war von 1993 bis 1997 einer der prägenden Veranstaltungsorte der Techno-Szene. Es war der erste richtig große Club in Berlin. Auf der anderen Seite der Wilhelmstraße ist heute das Finanzministerium. Der Umzug des Ministeriums nach Berlin war auch eine der Ursachen dafür, das das E-Werk 1997 schliessen musste. Die (legendären) Raves auf dem Parkplatz des E-Werks hätten die Beamten wohl zu sehr verunsichert.


Berlin 1998, 90°



Ein Flyer aus dem 90°.


Berlin 1997, WTF


Ein Flyer aus dem WTF.


Berlin 1999, Ostgut – Alles gut


Ein Flyer aus dem Ostgut.