One of the many to many relationships in this diagram is
items.sold_at and items.reviews.body.
The reason was
From an items point of view there are possibly Many values of sold_at and Many values of reviews.body .
So going from one of those two fields to another, we will traverse a Many-to-One relationship, then a One-to-Many relationship, making the whole relationship a Many-to-Many relationship.
Another way to look at it is to understand that a given review will be indirectly linked to all the stores that sell the product and that a given store has multiple reviews pertaining to the products it sells.
I don’t understand the “we will traverse a Many-to-One relationship, then a One-to-Many relationship”
I believe the “Many-to-One” relationship is referring to the relationship between the store ids in the items.sold_at array and the items entities but isn’t that a many-to-many relationship? Any given store can have multiple items and any given item can be sold at multiple stores right?