从逻辑上思考数据库结构：为用户发布的内容添加“标签” - 单独的表格或......？

I'm still beginning to get my head around this whole relational-database-thingymawhatsit. Anyway, I'm a PHP programmer so I can do all that shabang. I just need to think what would be the best method for this scenario...I'm still beginning to get my head around this