ERD: Relationship Cardinalities

[adriannafenee]

Thanks, Dustin! This is exactly what I needed for today's exam. I dont know why those crows feet were giving me such a hard time but thank you for this breakdown! LOL

[huda]

I have a midterm tommorow on this chapter and you honestly put together everything, it made sense, it had all the content I needed to learn. thank you so much truly. It is hard enough to find content when you are a university student and i appreciate your efforts!! :) stay blessed. 😁

[enviousshade]

why do you sound like chris chan it took me a while to concentrate because of this😂😂

[HemantaShrestha-zmdc]

how would you describe unary many to many relationship on table, in context of referencing ?

[TheAbsoluteSir]

I think a game can definitely be within multiple seasons in a different year! However, within the same year, a game will only ever be in one season, like how Basketball is in winter. I feel like either answer is fine, but you have to make sure you have words between tables to help understand the relationship/

[devakinandan]

I'd argue that players might not always need coaching and might self train as well, so it is probably optional-many. Anyways, excellent video, made me understand the concept pretty well. Thank you, justin

[dyllgood]

Hey Dustin, thanks for the information.
Just one question... On the One-to-Many (1:M) Unary Raltionship example, if the relationship cardinality was flipped, would that mean there are many managers for 1 singular person? In other words, does the relationship change based on which cardinality is on the bottom or side?

[primordialquasar]

Hi Dustin. What's the point of optional relationships from a database standpoint.

Example: EMPLOYEE manages DEPARTMENT.
An employee doesn't need to manage a department, so DEPARTMENT is optional to EMPLOYEE.

But if it was wrongly identified as mandatory instead and an employee must manage a department, does that mean when an employee is created in the EMPLOYEE table, a row in the DEPARTMENT table must exist to associate the two (like some kind of dummy entry)?

This is purely from a database standpoint. I just don't understand why a dummy entry needs to be created if it was wrongly identified as mandatory if it was actually in fact optional.

[ratminurisnaini]

Hello Dustin, I'd like to ask. If we want to connect two entities with relationship, should we have the same attributes in each entities? For example I have attribute A as a primary key in entity 1 and attribute A as a foreign key in entity 2, then I can connect these entity 1 and 2. But how if I don't have attribute A in entity 2. Can I still connect entity 1 and 2?

[HemantaShrestha-zmdc]

how would you describe unary many to many relationship on table, in context of referencing ?