Basic Entity Relationship Models

Рет қаралды 6,434

Жыл бұрын

A discussion of entity relationship models and their associated diagrams in the planning/designing of databases. Entities, attributes, and relationships are discussed, as well as relationship cardinality, participation (total vs partial), and degree (unary, binary, n-ary).

Пікірлер: 12

@MrCArthurMO 6 ай бұрын

You explained this much better than my teacher. Thank you very much for the educational content!

@tylerpotter8460 10 ай бұрын

This was so well done! I'm genuinely impressed. Thank you for putting this together!

@kevharv 4 ай бұрын

I love the song choices lol

@88564894654984561653 Жыл бұрын

10/10 as usual

@deemasafwan3493 7 ай бұрын

wonderful

@georgec.2857 10 ай бұрын

Can we say that the Entity Album is weak and is dependent on the entity Song? As an album can only exist if it has songs in it, but a song can exist without it being in an album no?

@JacobSchrum 8 ай бұрын

Weak entity instances need to be associated with exactly one instance of the strong entity that owns them, so they cannot be in a many-to-many relationship. Therefore, the Album must be a strong entity.

@MountainMan-ri2lr 5 ай бұрын

I think Artist could be a composite attribute composed of something like "primary artist" and "featured"

@living_curious Жыл бұрын

What about when one song is the first song of multiple artists? Will the relation still remain 1-to-1 or m-to-1

@JacobSchrum Жыл бұрын

There are several assumptions in the model that make this not possible. Every song is sung by exactly one artist. There can be one artist and multiple featured artists, but with only one artist associated with each song, it would not be possible for multiple artists to have the same first song. In this model, a song corresponds to a specific recording of the song, so multiple people may have their own version of the same lyrics, but ultimately a specific recording of a song belongs to only one artist.