Site And Database Design

The application I am making requires several types of data. For example: Pages, Categories, Products, Links

What I need in the end is to create router that will looks like


which will access any of the content I mentioned.

So I create one table (ex. nodes) which will contain all the site data (Pages, Categories, Products, Links), and each record will has a type field which will contain the node type.

And here comes the problem: some of the data types will require some additional fields, for example Products will need to have price,size,quantity …

I will accept any working idea.

Thanks in advance