Chapter 2 : Lab: Many-to-Many Relationship

A few questions as not sure im understanding what im looking at correctly

Stores[200], items[10] etc etc what is the number in brackets on the entity titles for? Are these arrays, or something else, like number of documents in a collection?

What do the two vertical lines mean on the line ending at users?

Do the empty circles represent optional, as in zero, one or many multiplicity?

Many thanks

Revisit *** Chapter 2: Relationships - Relationship Types and Cardinality***, it is all there.

We do not know. These are the relation. Designing the schema will answer that question.

I checked out the document about ERDs and answered some of my questions. I couldn’t see an answer about the Stores[200] etc question. It must mean something, how does designing the schema help understand Stores[200]?

To me it looks like the number of items in the collection.

This video seems to explain it:

I had watched it before, but hadn’t remembered.