An article about how to model hierarchical data in a relational database (specifically MySQL, but likely also applying to other relational DBMS). Originally, this article was on the MySQL developement site, and linked heavily as `http://dev.mysql.com/tech-resources/articles/hierarchical-data.html`. But now Oracle (which owns MySQL after buying Sun, which itself bought MySQL some years ago) seems to have reorganized its site, with the effect that this link goes only to an Oracle search page. This was remarked by some anonymous Stack Overflow user, who suggested the following [edit][] to an answer linking to this page: > -- UPDATE: The link is dead. Thanks Oracle. -- I saw this edit suggestion by browsing through the list of suggested edits, and thought *this article should not have been completely gone away*. [Googleing the URL][google-url] did not really result in finding the current location of the article (only in some pages linking to the original one). A good idea in such cases is the *Wayback Machine* of the [Internet Archive][]. It stores previous versions of lots of pages - [this one, too (last accessed in January 2010)][jan-2010]. If I only wanted to read the old article, this would be enough - but no, I in fact want to correct the link, and it is not a good idea to link to the Wayback machine. But having the article itself, it was easy to copy a sampe sentence to Google, which finally found me the [new location][] of the article (on the web site of its original author). Thus I edited this [answer][] to include the new link (and the *title* of the article). A short [google search for the original URL on stackoverflow alone][google-so] shows that the link was quite popular. So I started an editing spree, starting to replace each occurrence of this link with the new one. I always try to correct other issues with the post, as well, or course. Have a look at my [activity log][] to see how many edits I had to do for this (most entries with *revised*, starting at 16:15 UTC today). [edit]: http://stackoverflow.com/suggested-edits/86358 [google-url]: http://www.google.com/search?q=http://dev.mysql.com/tech-resources/articles/hierarchical-data.html [Internet Archive]: http://www.archive.org/ [jan-2010]: http://web.archive.org/web/20100105135622/http://dev.mysql.com/tech-resources/articles/hierarchical-data.html [new location]: http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/ [answer]: http://stackoverflow.com/q/3438663/600500 [google-so]: http://www.google.com/search?q=http://dev.mysql.com/tech-resources/articles/hierarchical-data.html [activity log]: http://stackoverflow.com/users/600500/paulo-ebermann?tab=activity