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

Frequently Asked Questions SQL FAQ
1

Community%20FAQs%20on%20Codecademy%20Exercises
Community%20FAQs%20on%20Codecademy%20Exercises1000×208 141 KB

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

Paths and Courses
This exercise can be found in the following Codecademy content:

Design Databases With PostgreSQL

FAQs on the exercise One-to-Many Relationship

There are currently no frequently asked questions associated with this exercise – that’s where you come in! You can contribute to this section by offering your own questions, answers, or clarifications on this exercise. Ask or answer a question by clicking reply (reply) below.

If you’ve had an “aha” moment about the concepts, formatting, syntax, or anything else with this exercise, consider sharing those insights! Teaching others and answering their questions is one of the best ways to learn and stay sharp.

Join the Discussion. Help a fellow learner on their journey.

Ask or answer a question about this exercise by clicking reply (reply) below!
You can also find further discussion and get answers to your questions over in Language Help.

Agree with a comment or answer? Like (like) to up-vote the contribution!

Need broader help or resources? Head to Language Help and Tips and Resources. If you are wanting feedback or inspiration for a project, check out Projects.

Looking for motivation to keep learning? Join our wider discussions in Community

Learn more about how to use this guide.

Found a bug? Report it online, or post in Bug Reporting

Have a question about your account or billing? Reach out to our customer support team!

None of the above? Find out where to ask other questions here!

2

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?

image
image4167×2084 233 KB

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.

Thanks

3

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.