ER Diagram
Basic schema
Unique constraints ?
I am somewhat confused by what exactly school of Located_at or school of Principle_of is meant to be? I understand the idea here is to denote the 1..1 cardinality by enforcing uniqueness but isn't the uniqueness inherent by the choice of key ( excluding weak entity sets ) as it being the unique identifier? In other words, for example with Located_at why isn't the schema just Located_at(*address_id* -> Address, name -> Preschool) in what way does school -> Preschool differ from that or is it just some kind of alias for the key ?
Same applies to the other choices of worker, principle, child ? They don't appear to be keys of any kind so I don't exactly understand what they are ?
I just started my DB course so I am very new to all this, I apologize if this is just me missing some fundamentals.
