I'm planning db for my some web app. And I find confusing one thing about common table for several tables, for example:
Each row from table
You should use something like
Now you create a table IMAGE(ID,Image_Blob, ...)
And mapping tables like
All columns with Foreign Key Constraints and index.
Maybe you get the advise to use a common mapping table with an additional
LinkingTo column where you put the source table's name. But doing so, you'd have to trick around with foreign key constraints.
It is an almost general rule: Good databases have many tables :-)