Do you mean for automatically assigning IDs? The only other common practice is to generate a id in such a way that in high likelihood is unique. MongDB uses timestamp, random value, and counter
What did you have in mind?
"Oppenheimer" is an entity and so is Barbie, and
they are both in the Movie
table, which is an entity
set. That's the traditional terminology. (It's also traditional
to use singular words, which also makes queries a little easier to
read.)
However, there are lots of contexts were the words are used less carefully.
A set is just like the use in mathematics: a collection of things.
The boxes in the ER diagram represent sets of entities. The lines represent sets of lines.
Well, we've seen some examples in the ER diagram. W3 schools has some more. And we can look at the MySQL Syntax
We could make the relationship many-to-many. I decided against this, mostly because I wanted a good example example of a 1-to-many relationship.
We don't enter data using dbdiagram.io. We enter it in the usual way: ad hoce INSERT statements, CSV files, and, very soon, web applications.
Let's draw out an example:
Collectively, we have a many-to-many relationship between actors and movies
Sure! I'll probably stick to the on-campus vs off-campus student example, but as an exercise, figure out how you'd represent something like university info
We haven't seen any examples of ISA. It might come up in your projects, though.
It might be possible to infer an ISA relationship from a ER diagram, but I would strongly suggest supplementing the ER diagram with textual documentation. Don't lean too heavily on tools and notation.
Convenience, storage, and efficiency. In fact, in my diabetes project, we have two different approaches.