Unique constraint Memes

The classic "just one small change" that breaks your entire data model. You design a perfect database with a unique constraint ensuring each user belongs to exactly one organization. The requirements were crystal clear. You even got it in writing. Then suddenly, the user who SWORE the relationship would "always be N:1" comes back asking if users can belong to multiple organizations. That look of horror is every database architect who now has to create a junction table, update all the queries, and pretend they're not dying inside. Next time, just assume every relationship is many-to-many from the start and save yourself the trauma.

When your database schema is so bad that you're using age as a primary key. Because apparently, birthdays are more unique than usernames! Bonus points for the error message implying there's only ONE 17-year-old allowed on the platform. That dev probably also stores passwords in plaintext and thinks SQL injection is a new energy drink.

Ah, the classic primary key violation that no one warned the poor user about. Some developer thought storing age as a unique identifier was a brilliant idea, and now we've got 17-year-olds fighting in the Thunderdome for database supremacy. Next time try using UUID instead of, you know, THE MOST COMMON AGE AMONG TEENAGE USERS. This is what happens when you let the intern design your database schema after a Red Bull all-nighter.