29.04.2014, 07:12
Nothing. It's just bad practice and usually an indication that your database isn't properly normalized and that you aren't using MySQL correctly. Once particular data duplicates across multiple tables then that data should be linked from a separate table. Say, if you identify a player's properties by name. If the player changes his name you'd need to update it in their account, in the houses table, in the business table, and wherever else it might be used.