sqldatabase-designrelational-databaseentity-relationship
Simple Multiplicity in Relational Database ER Diagram
I'm trying to design a database for a duty roster but i'm struggling with the multiplicity on the ER diagram.
Here is the section i'm struggling with:
The DutyRoster table in the database will act as a huge link table that joins the members with an event and a duty.
Therefore, it will contain many records for each staff member, many for each records per event (one for each staff member) and many records for each duty. How is this represented using the multiplicity? Is each link a many-to-many relationship?
Solution
As you've currently modelled this (with the FK's), an Instance DutyRoster consists of exactly one Event, one Staff-member and one EventDuty.
As I'm understanding this whole ER, the multiplicities should be as follows:
DutyRoster * -------- 1 Event
DutyRoster * -------- 1 Staff
DutyRoster * -------- 1 EventDuty
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