FAQ: What Are Database Relationships? - One-to-Many Relationship

This community-built FAQ covers the “One-to-Many Relationship” exercise from the lesson “What Are Database Relationships?”.

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This exercise can be found in the following Codecademy content:

Design Databases With PostgreSQL

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Hello Codecademy Forum,

Can somebody explain to me how the image shown in the exercise “One-to-Many Relationship,” shows one-to-many? To me it looks like there is one person.id linked to one email.person_id?

I think I understand the concept, that there can be no greater than one person.id but there can be many references to it via email.person_id with ‘many’ different email account tables. I just find the image a little confusing as there is only a single connection shown, and I have to imagine extra little email tables.

Please let me know if i’m missing anything.


I think the database schema illustrations used in this lesson are not written to be able to distinguish between one-to-one and one-to-many relationships. One way to distinguish between them is to draw some symbols at both ends of lines connecting tables. I’ve seen such figures, but I don’t know there is any rule of format. They might be borrowed from entity relationship diagrams.

It’s a mistake to think of multiple email tables. There is one email table, but there are multiple rows in the table. ‘One-to-many’ means multiple rows in the email table can have the same person_id.