A few years back I worked at a company as their front-end web developer with one other guy who was their "back-end" developer. PHP and MySQL specifically. He was eventually fired and I took over both development roles. When I got around to seeing his source code and the way he had created the databases, I immediately saw why he was fired. This guy did not understand the concept of loops. Instead of separating out tags and categories with a split / loop, he set up database tables for EVERY. SINGLE. TAG.
i.e. tag_1, tag_2, tag_3, etc. And then to top ot off, instead of looping through the tables, he set up huge conditioks for EVER.LY. SINGLE. TAG.
i.e. if(tag_1) else(tag_2) else(tag_3) etc.

That fucking guy...