In general, I always use Ints. I know that in theory this is not the best practice, though, since you should use the smallest data type that will be guaranteed to store the data. For example, it's ...
Where can I find ready-to-use database models ? I don't need a database with data in it, but only schemas (UML diagrams). Perhaps something like the data models at this link, but much more complex ...
As I understand it, polymorphic relationships among tables in a database allow one table to have one foreign key that references many tables. I have found that tags are a common application of this ...
Looking at the name Data Manipulation Language (DML) I would assume, that all contained statements are actually for manipulating data. As far as I know the SELECT statement can only be used to query ...