CODEWITHSUNDEEP
database
shaun022
shaun022

Reputation: 3

can a relationship between a weak entity set and a strong entity set be many-to-many?

Everywhere I've searched it's just saying that the relationship is one-to-many from strong entity to weak entity, but never exactly explained "why".

I mean, I don't understand why it can't be many-to-many. Those "many" entities from the weak entity set can map to "one" entity from the strong entity set, but "many" entities from strong entity set can also map to just "one" entity in the weak entity set (in my opinion); what's wrong with that?

Upvotes: 0

Views: 1939

Answers (1)

K.Nicholas
K.Nicholas

Reputation: 11561

How are you going to add a key from the weak entity to the strong entity? That's why you can't have many Strong entities mapping to the Weak entity. In order to do so, the Strong entity would need the primary key of the Weak entity, but a Weak entity does not have its own primary key. A Weak entity is defined as an entity with primary keys made of other entities' primary keys. E.g.

Strong vs Weak entities MYSQL

Also, see diagram:

enter image description here

Upvotes: 0

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